Another curious illustration of the skill with which the Scotch mind,

when once possessed of a principle, worked from it deductively, appears

in the geological speculations of Hutton, late in the eighteenth century.

It is well known, that the two great powers which have altered the

condition of our planet, and made it what it is, are fire and water. Each

has played so considerable a part, that we can hardly measure their

relative importance. Judging, however, from the present appearance of the

crust of the earth, there is reason to believe, that the older rocks are

chiefly the result of fusion, and that the younger are aqueous deposits.

It is, therefore, not unlikely, that, in the order in which the energies

of nature have unfolded themselves, fire preceded water, and was its

necessary precursor.[780] But, all that we are as yet justified in

asserting is, that these two causes, the igneous and the aqueous, were in

full operation long before man existed, and are still busily working.

Perhaps they are preparing another change in our habitation, suitable to

new forms of life, as superior to man, as man is superior to the beings

who occupied the earth before his time. Be this as it may, fire and water

are the two most important and most general principles with which

geologists are concerned; and though, on a superficial view, each is

extremely destructive, it is certain that they can really destroy

nothing, but can only decompose and recompose; shifting the arrangements

of nature, but leaving nature herself intact. Whether one of these

elements will ever again get the upper hand of its opponent, is a

speculation of extreme interest. For, there is reason to suspect, that,

at one period, fire was more active than water, and that, at another

period, water was more active than fire. That they are engaged in

incessant warfare, is a fact with which geologists are perfectly

familiar, though, in this, as in many other cases, the poets were the

first to discern the truth. To the eye of the geologist, water is

constantly labouring to reduce all the inequalities of the earth to a

single level; while fire, with its volcanic action, is equally busy in

restoring those inequalities, by throwing up matter to the surface, and

in various ways disturbing the crust of the globe.[781] And as the beauty

of the material world mainly depends on that irregularity of aspect,

without which scenery would have presented no variety of form, and but

little variety of colour, we shall, I think, not be guilty of too refined

a subtlety, if we say that fire, by saving us from the monotony to which

water would have condemned us, has been the remote cause of that

development of the imagination which has given us our poetry, our

painting, and our sculpture, and has thereby not only wonderfully

increased the pleasures of life, but has imparted to the human mind a

completeness of function, to which, in the absence of such a stimulus, it

could not have attained.

[780] The supposition, that volcanic agencies were formerly more potent

than they are now, is by no means inconsistent with the scientific

doctrine of uniformity, though it is generally considered to be

so. It is one thing to assert the uniformity of natural laws; it

is quite another thing to assert the uniformity of natural causes.

Heat may once have produced far greater effects than it can do at

present, and yet the laws of nature be unchanged, and the order

and sequence of events unbroken. What I would venture to suggest

to geologists is, that they have not taken sufficiently into

account the theory of the interchange of forces, which seems to

offer a solution of at least part of the problem. For, by that

theory, a large portion of the heat which formerly existed may

have been metamorphosed into other forces, such as light, chemical

affinity, and gravitation. The increase of these forces consequent

on the diminution of heat, would have facilitated the

consolidation of matter; and until such forces possessed a certain

energy, water, which afterwards became so prominent, could not

have been formed. If the power of chemical affinity, for instance,

were much weaker than it is, water would assuredly resolve itself

into its component gases. Without wishing to lay too much stress

on this speculation, I submit it to the consideration of competent

judges, because I am convinced that any hypothesis, not absolutely

inconsistent with the known laws of nature, is preferable to that

dogma of interference, which what may be called the miraculous

school of geologists wish to foist upon us, in utter ignorance of

its incompatibility with the conclusions of the most advanced

minds in other departments of thought.

The remarks in Sir Roderick Murchison's great work (_Siluria_,

London, 1854, pp. 475, 476) on the 'grander intensity of former

causation,' and on the difficulty this opposes to the

'uniformitarians,' apply merely to those who take for granted that

_each_ force has always been equally powerful: they do not affect

those who suppose that it is only the _aggregate_ of force which

remains unimpaired. Though the distribution of forces may be

altered, their gross amount is not susceptible of change, so far

as the highest conceptions of our actual science extend.

Consequently, there is no need for us to believe that, in

different periods, the intensity of causation varies; though we

may believe that some one agent, such as heat, had at one time

more energy than it has ever had since.

[781] 'The great agents of change in the inorganic world may be divided

into two principal classes, the aqueous and the igneous. To the

aqueous belong rain, rivers, torrents, springs, currents, and

tides; to the igneous, volcanos and earthquakes. Both these

classes are instruments of decay as well as of reproduction; but

they may also be regarded as antagonist forces. For the aqueous

agents are incessantly labouring to reduce the inequalities of the

earth's surface to a level; while the igneous are equally active

in restoring the unevenness of the external crust, partly by

heaping up new matter in certain localities, and partly by

depressing one portion, and forcing out another, of the earth's

envelope.' _Lyell's Principles of Geology_, 9th edit., London,

1853, p. 198.

When geologists began to study the laws according to which fire and water

had altered the structure of the earth, two different courses were open

to them, namely, the inductive and the deductive. The deductive plan was

to compute the probable consequences of fire and water, by reasoning from

the sciences of thermotics and hydrodynamics; tracking each element by an

independent line of argument, and afterwards coördinating into a single

scheme the results which had been separately obtained. It would then only

remain to inquire, how far this imaginary scheme harmonized with the

actual state of things; and if the discrepancy between the ideal and the

actual were not greater than might fairly be expected from the

perturbations produced by other causes, the ratiocination would be

complete, and geology would, in its inorganic department, become a

deductive science. That our knowledge is ripe for such a process, I am

far, indeed, from supposing; but this is the path which a deductive mind

would take, so far as it was able. On the other hand, an inductive mind,

instead of beginning with fire and water, would begin with the effects

which fire and water had produced, and would first study these two

agents, not in their own separate sciences, but in their united action as

exhibited on the crust of the earth. An inquirer of this sort would

assume, that the best way of arriving at truth would be to proceed from

effects to causes, observing what had actually happened, and rising from

the complex results up to a knowledge of the simple agents, by whose

power the results have been brought about.

If the reader has followed the train of thought which I have endeavoured

to establish in this chapter, and in the first volume, he will be

prepared to expect that when, in the latter half of the eighteenth

century, geology was first seriously studied, the inductive plan of

proceeding from effects to causes became the favourite one in England;

while the deductive plan of proceeding from causes to effects, was

adopted in Scotland and in Germany. And such was really the case. It is

generally admitted, that, in England, scientific geology owes its origin

to William Smith, whose mind was singularly averse to system, and who,

believing that the best way of understanding former causes was to study

present effects, occupied himself, between the years 1790 and 1815, in a

laborious examination of different strata.[782] In 1815, he, after

traversing the whole of England on foot, published the first complete

geological map which ever appeared, and thus took the first great step

towards accumulating the materials for an inductive generalization.[783]

In 1807, and, therefore, before he had brought his arduous task to an

end, there was formed in London the Geological Society, the express

object of which, we are assured, was, to observe the condition of the

earth, but by no means to generalize the causes which had produced that

condition.[784] The resolution was, perhaps, a wise one. At all events,

it was highly characteristic of the sober and patient spirit of the

English intellect. With what energy and unsparing toil it has been

executed, and how the most eminent members of the Geological Society

have, in the pursuit of truth, not only explored every part of Europe,

but examined the shell of the earth in America and in Northern Asia, is

well known to all who are interested in these matters; nor can it be

denied, that the great works of Lyell and Murchison prove that the men

who are capable of such laborious enterprises, are also capable of the

still more difficult achievement of generalizing their facts and refining

them into ideas. They did not go as mere observers, but they went with

the noble object of making their observations subservient to a discovery

of the laws of nature. That was their aim; and all honour be to them for

it. Still, it is evident, that their process is essentially inductive; it

is a procedure from the observation of complex phenomena, up to the

elements to which those phenomena are owing; it is, in other words, a

study of natural effects, in order to learn the operation of natural

causes.

[782] Dr. Whewell, comparing him with his great German contemporary,

Werner, says, 'In the German, considering him as a geologist, the

ideal element predominated.' ... 'Of a very different temper and

character was William Smith. No literary cultivation of his youth

awoke in him the _speculative love of symmetry and system_; but a

singular clearness and precision of the classifying power, which

he possessed as a native talent, was exercised and developed by

exactly those geological facts among which his philosophical task

lay.' ... 'We see great vividness of thought and activity of mind,

_unfolding itself exactly in proportion to the facts with which it

had to deal_.' ... 'He dates his attempts to discriminate and

connect strata from the year 1790.' _Whewell's History of the

Inductive Sciences_, London, 1847, vol. iii. pp. 562-564.

[783] 'The execution of his map was completed in 1815, and remains a

lasting monument of original talent and extraordinary

perseverance; for he had explored the whole country on foot

without the guidance of previous observers, or the aid of

fellow-labourers, and had succeeded in throwing into natural

divisions the whole complicated series of British rocks.' _Lyell's

Principles of Geology_, p. 58. Geological maps of parts of England

had, however, been published before 1815. See _Conybeare on

Geology_, in _Second Report of the British Association_, p. 373.

[784] 'A great body of new data were required; and the Geological

Society of London, founded in 1807, conduced greatly to the

attainment of this desirable end. To multiply and record

observations, and patiently to await the result at some future

period, was the object proposed by them; and it was their

favourite maxim, that the time was not yet come for a general

system of geology, but that all must be content for many years to

be exclusively engaged in furnishing materials for future

generalizations.' _Lyell's Principles of Geology_, p. 59. Compare

_Richardson's Geology_, 1851, p. 40.

Very different was the process in Germany and Scotland. In 1787, that is,

only three years before William Smith began his labours, Werner, by his

work on the classification of mountains, laid the foundation of the

German school of geology.[785] His influence was immense; and among his

pupils we find the names of Mohs, Raumer, and Von Buch, and even that of

Alexander Humboldt.[786] But the geological theory which he propounded,

depended entirely on a chain of argument from cause to effect. He

assumed, that all the great changes through which the earth had passed,

were due to the action of water. Taking this for granted, he reasoned

deductively from premisses with which his knowledge of water supplied

him. Without entering into details respecting his system, it is enough to

say, that, according to it, there was originally one vast and primeval

sea, which, in the course of time, deposited the primitive rocks. The

base of all was granite; then gneiss; and others followed in their

order. In the bosom of the water, which at first was tranquil, agitations

gradually arose, which, destroying part of the earliest deposits, gave

birth to new rocks, formed out of their ruins. The stratified thus

succeeded to the unstratified, and something like variety was

established. Then came another period, in which the face of the waters,

instead of being merely agitated, was convulsed by tempests, and, amid

their play and collision, life was generated, and plants and animals

sprung into existence. The vast solitude was slowly peopled, the sea

gradually retired; and a foundation was laid for that epoch, during which

man entered the scene, bringing with him the rudiments of order and of

social improvement.[787]

[785] Cuvier, in his Life of Werner, says (_Biographie Universelle_,

vol. i. pp. 376, 377), 'La connaissance des positions respectives

des minéraux dans la croûte du globe, et ce que l'on peut en

conclure relativement aux époques de leur origine, forment une

autre branche de la science qu'il appelle Géognosie. Il en

présenta les premières bases en 1787, dans un petit écrit intitulé

"Classification et description des Montagnes."'

[786] _Whewell's History of the Inductive Sciences_, vol. iii. p. 567.

[787] 'Une mer universelle et tranquille dépose en grandes masses les

roches primitives, roches nettement cristallisées, où domine

d'abord la silice. Le granit fait la base de tout; au granit

succède le gneiss, qui n'est qu'un granit commençant à se

feuilleter.' ... 'Des agitations intestines du liquide détruisent

une partie de ces premiers dépôts; de nouvelles roches se forment

de leurs débris réunis par des cimens. C'est parmi ces tempêtes

que naît la vie.' ... 'Les eaux, de nouveau tranquillisées, mais

dont le contenu a changé, déposent des couches moins épaisses et

plus variées, où les débris des corps vivans s'accumulent

successivement dans un ordre non moins fixe que celui des roches

qui les contiennent. Enfin, la dernière retraite des eaux répand

sur le continent d'immenses alluvions de matières meubles,

premiers sièges de la végétation, de la culture et de la

sociabilité.' _Eloge de Werner_, in _Cuvier_, _Recueil des Elogés

Historiques_, vol. ii. pp. 321-323.

These were the leading views of a system which, we must remember,

exercised great sway in the scientific world, and won over to its side

minds of considerable power. Erroneous and far-fetched though it was, it

had the merit of calling attention to one of the two chief principles

which have determined the present condition of our planet. It had the

further merit of provoking a controversy, which was eminently serviceable

to the interests of truth. For, the great enemy of knowledge is not

error, but inertness. All that we want is discussion, and then we are

sure to do well, no matter what our blunders may be. One error conflicts

with another; each destroys its opponent, and truth is evolved. This is

the course of the human mind, and it is from this point of view that the

authors of new ideas, the proposers of new contrivances, and the

originators of new heresies, are benefactors of their species. Whether

they are right or wrong, is the least part of the question. They tend to

excite the mind; they open up the faculties; they stimulate us to fresh

inquiry; they place old subjects under new aspects; they disturb the

public sloth; and they interrupt, rudely, but with most salutary effect,

that love of routine, which, by inducing men to go grovelling on in the

ways of their ancestors, stands in the path of every improvement, as a

constant, an outlying, and, too often, a fatal obstacle.

The method adopted by Werner was evidently deductive, since he argued

from a supposed cause, and reasoned from it to the effects. In that

cause, he found his major premiss, and thence he worked downwards to his

conclusion, until he reached the world of sense and of reality. He

trusted in his one great idea, and he handled that idea with consummate

skill. On that very account, did he pay less attention to existing facts.

Had he chosen, he, like other men, could have collected them, and

subjected them to an inductive generalization. But he preferred the

opposite path. To reproach him with this is irrational; for, in his

journey after truth, he chose one of the only two roads which are open to

the human mind. In England, indeed, we are apt to take for granted that

one road is infinitely preferable to the other. It may be so; but on

this, as on many other subjects, assertions are current which have never

been proved. At all events, Werner was so satisfied with his method, that

he would not be at the pains of examining the position of rocks and their

strata, as they are variously exhibited in different countries; he did

not even explore his own country, but, confining himself to a corner of

Germany, he began and completed his celebrated system, without

investigating the facts on which, according to the inductive method, that

system should have been built.[788]

[788] 'If it be true that delivery be the first, second, and third

requisite in a popular orator, it is no less certain that to

travel is of first, second, and third importance to those who

desire to originate just and comprehensive views concerning the

structure of our globe. Now, Werner had not travelled to distant

countries: he had merely explored a small portion of Germany, and

conceived, and persuaded others to believe, that the whole surface

of our planet, and all the mountain chains in the world, were made

after the model of his own province.' ... 'It now appears that he

had misinterpreted many of the most important appearances even in

the immediate neighbourhood of Freyberg. Thus, for example, within

a day's journey of his school, the porphyry, called by him

primitive, has been found not only to send forth veins, or dykes,

through strata of the coal formation, but to overlie them in

mass.' _Lyell's Principles of Geology_, p. 47.

Exactly the same process, on the same subject, and at the same time, was

going on in Scotland. Hutton, who was the founder of Scotch geology, and

who, in 1788, published his _Theory of the Earth_, conducted the inquiry

just as Werner did; though, when he began his speculations, he had no

knowledge of what Werner was doing.[789] The only difference between them

was, that while Werner reasoned from the agency of water, Hutton reasoned

from the agency of fire. The cause of this may, I think, be explained.

Hutton lived in a country where some of the most important laws of heat

had, for the first time, been generalized, and where consequently, that

department of inorganic physics had acquired great reputation. It was

natural for a Scotchman to take more than ordinary interest in a subject

in which Scotland had been so successful, and had obtained so much fame.

We need not, therefore, wonder that Hutton, who, like all men, felt the

intellectual bent of the time in which he lived, should have yielded to

an influence of which he was, perhaps, unconscious. In obedience to the

general mental habits of his country he adopted the deductive method. In

further obedience to the more special circumstances connected with his

own immediate pursuits, he gathered the principles from which he reasoned

from a study of fire, instead of gathering them, as Werner did, from a

study of water.

[789] Though Hutton's _Theory of the Earth_ was first published in 1788,

the edition of 1795, which is the one I have used, contains a

great number of additional illustrations of his views, and was

evidently re-written. But the main features are the same; and we

learn from his friend, Playfair, that 'the great outline of his

system' was completed 'several years' before 1788. _Life of

Hutton_, in _Playfair's Works_, vol. iv. p. 50, Edinburgh, 1822.

Hence it is, that, in the history of geology, the followers of Werner are

known as Neptunists, and those of Hutton as Plutonists.[790] And these

terms represent the only difference between the two great masters. In the

most important points, namely their method, they were entirely agreed.

Both were essentially one-sided; both paid a too exclusive attention to

one of the two principal agents which have altered, and are still

altering, the crust of the earth; both reasoned from those agents,

instead of reasoning to them; and both constructed their system without

sufficiently studying the actual and existing facts; committing, in this

respect, an error which the English geologists were the first to rectify.

[790] Kirwan appears to have been the first who called Hutton's theory

'the Plutonic System.' See _Illustrations of the Huttonian

Theory_, in _Playfair's Works_, vol. i. p. 145. On the distinction

between Neptunists and Plutonists, see the same work, pp. 504,

505.

As I am writing a history, not of science, but of scientific method, I

can only briefly glance at the nature of those services which Hutton

rendered to geology, and which are so considerable, that his system has

been called its present basis.[791] This, however, is too strongly

expressed; for, though Hutton was far from denying the influence of

water,[792] he did not concede enough to it, and there is a tendency

among several geologists to admit that the system of Werner considered

as an aqueous theory, contains a larger amount of truth than the

advocates of the igneous theory are willing to allow. Still, what Hutton

did was most remarkable, especially in reference to what are now termed

metamorphic rocks, the theory of whose formation he was the first to

conceive.[793] Into this, and into their connexion, on the one hand, with

the sedimentary rocks, and, on the other hand, with those rocks whose

origin is perhaps purely igneous, I could not enter without treading on

debatable ground. But, putting aside what is yet uncertain, I will

mention two circumstances respecting Hutton which are undisputed, and

which will give some idea of his method, and of the turn of his mind. The

first circumstance is, that, although he ascribed to subterranean heat,

as exhibited in volcanic action, a greater and more constant energy than

any previous inquirers had ventured to do,[794] he preferred speculating

on the probable consequences of that action, rather than drawing

inferences from the facts which the action presented; he being on this

point so indifferent, that he arrived at his conclusions without

inspecting even a single region of active volcanoes, where he might have

watched the workings of nature, and seen what she was really about.[795]

The other circumstance is equally characteristic. Hutton, in his

speculations concerning the geological effects of heat, naturally availed

himself of the laws which Black had unfolded. One of those laws was, that

certain earths owe their fusibility to the presence of fixed air in them

before heat has expelled it; so that if it were possible to force them to

retain their fixed air, or carbonic acid gas, as we now call it, no

amount of heat could deprive them of the capability of being fused. The

fertile mind of Hutton saw, in this discovery, a principle from which he

could construct a geological argument. It occurred to him, that great

pressure would prevent the escape of fixed air from heated rocks, and

would thus enable them to be fused, notwithstanding their elevated

temperature. He then supposed that, at a period anterior to the existence

of man, such a process had taken place under the surface of the sea, and

that the weight of so great a column of water had prevented the rocks

from being decomposed while they were subjected to the action of fire. In

this way, their volatile parts were held together, and they themselves

might be melted, which could not have happened except for this enormous

pressure. By following this line of argument, he accounted for the

consolidation of strata by heat; since, according to the premisses from

which he started, the oily, or bituminous parts, would remain, in spite

of the efforts of heat to disperse them.[796] This striking speculation

led to the inference, that the volatile components of a substance, and

its fixed components, may be made to cohere, in the very teeth of that

apparently irresistible agent whose business it is to effect their

separation. Such an inference was contrary to all experience; or, to say

the least, no man had ever seen an instance of it.[797] Indeed, the

event was only supposed to happen in consequence of circumstances which

were never met with on the surface of the globe, and which, therefore,

were out of the range of all human observation.[798] The utmost that

could be expected was, that, by means of our instruments, we might,

perhaps, on a small scale, imitate the process which Hutton had imagined.

It was possible, that a direct experiment might artificially combine

great pressure with great heat, and that the result might be, that the

senses would realize what the intellect had conceived.[799] But the

experiment had never been tried, and Hutton, who delighted in reasoning

from ideas rather than from facts, was not likely to undertake it.[800]

He cast his speculation on the world, and left it to its fate.[801]

Fortunately, however, for the reception of his system, a very ingenious

and skilful experimenter of that day, Sir James Hall, determined to test

the speculation by an appeal to facts; and as nature did not supply the

facts which he wanted, he created them for himself. He applied heat to

powdered chalk, while, at the same time, with great delicacy of

manipulation, he subjected the chalk to a pressure about equal to the

weight of a column of water half a mile high. The result was, that, under

that pressure, the volatile parts of the chalk were held together; the

carbonic acid gas was unable to escape; the generation of quicklime was

stopped; the ordinary operations of nature were baffled, and the whole

composition, being preserved in its integrity, was fused, and, on

subsequently cooling, actually crystallized into solid marble.[802]

Never was triumph more complete. Never did a fact more fully confirm an

idea.[803] But, in the mind of Hutton, the idea preceded the fact by a

long interval; since, before the fact was known, the theory had been

raised, and the system which was built upon it had, indeed, been

published several years. It, therefore, appears that one of the chief

parts of the Huttonian Theory, and certainly its most successful part,

was conceived in opposition to all preceding experience; that it

pre-supposed a combination of events which no one had ever observed, and

the mere possibility of which nothing but artificial experiment could

prove; and, finally, that Hutton was so confident of the validity of his

own method of inquiry, that he disdained to make the experiment himself,

but left to another mind that empirical branch of the investigation which

he deemed of little moment, but which we, in England, are taught to

believe is the only safe foundation of physical research.[804]

[791] 'Has not only supplanted that of Werner, but has formed the

foundation of the researches and writings of our most enlightened

observers, and is justly regarded as the basis of all sound

geology at the present day.' _Richardson's Geology_, London, 1851,

p. 38.

[792] _Hutton's Theory of the Earth_, Edinb. 1795, vol. i. pp. 34, 41,

192, 290, 291, 593, vol. ii. pp. 236, 369, 378, 555.

[793] 'In his writings, and in those of his illustrator, Playfair, we

find the germ of the metamorphic theory.' _Lyell's Manual of

Geology_, London, 1851, p. 92.

[794] The shortest summary of this view is in his _Theory of the Earth_,

Edin. 1795, vol. ii. pp. 556. 'The doctrine, therefore, of our

Theory is briefly this; that whatever may have been the operation

of dissolving water, and the chemical action of it upon the

materials accumulated at the bottom of the sea, the general

solidity of that mass of earth, and the placing of it in the

atmosphere above the surface of the sea, has been the immediate

operation of fire or heat melting and expanding bodies.'

[795] 'Although Hutton had never explored any region of active volcanos,

he had convinced himself that basalt and many other trap rocks

were of igneous origin.' _Lyell's Principles of Geology_, London,

1853, p. 51. To this I may add, that he wrote his work without

having examined granite. He says (_Theory of the Earth_, vol. i.

p. 214), 'It is true, I met with it on my return by the east

coast, when I just saw it, and no more, at Peterhead and Aberdeen;

but that was all the granite I had ever seen when I wrote my

_Theory of the Earth_. I have, since that time, seen it in

different places; because I went on purpose to examine it, as I

shall have occasion to describe in the course of this work.'

Hutton's theory of granite is noticed in _Bakewell's Geology_,

London, 1838, p. 101: but Mr. Bakewell does not seem to be aware

that the theory was formed before the observations were made.

[796] _Huttonian Theory_, in _Playfair_, vol. i. pp. 38-40, 509, 510.

Compare _Playfair's Life of Hutton_, p. 61.

[797] Hence, the objections of Kirwan were invalid; because his argument

against Hutton was 'grounded on experiments, where that very

separation of the volatile and fixed parts takes place, which it

excluded in that hypothesis of subterraneous heat.' HUTTONIAN

THEORY, in _Playfair_, vol. i. p. 193, Edinb. 1822.

[798] Hutton says (_Theory of the Earth_, Edinb. 1795, vol. i. p. 94),

'The place of mineral operations is not on the surface of the

earth; and we are not to limit nature with our imbecility, or

estimate the powers of nature by the measure of our own.' See also

p. 159, 'mineral operations proper to the lower regions of the

earth.' And p. 527, 'The mineral operations of nature lie in a

part of the globe which is necessarily inaccessible to man, and

where the powers of nature act under very different conditions

from those which we find take place in the only situation where we

can live.' Again, in vol. ii. p. 97, 'The present Theory of the

Earth holds for principle that the strata are consolidated in the

mineral regions far beyond the reach of human observation.'

Similarly, vol. ii. p. 484, 'we judge not of the progress of

things from the actual operations of the surface.'

[799] Hutton, however, did not believe that this could be done. 'In the

Theory of the Earth which was published, I was anxious to warn the

reader against the notion that subterraneous heat and fusion could

be compared with that which we induce by our chemical operations

on mineral substances here upon the surface of the earth.'

_Hutton's Theory of the Earth_, vol. i. p. 251.

[800] See, in the _Life of Hutton_, in _Playfair's Works_, vol. iv.

p. 62 note, a curious remark on his indifference to experimental

verification. Innumerable passages in his work indicate this

tendency, and show his desire to reason immediately from general

principles. Thus, in vol. i. p. 17, 'Let us strictly examine our

principles in order to avoid fallacy in our reasoning.' ... 'We

are now, in reasoning from principles, come to a point decisive of

the question.' vol. i. p. 177. 'Let us now reason from our

principles.' vol. ii. p. 308. Hence, his constantly expressed

contempt for experience; as in vol. ii. p. 367, where he says that

we must 'overcome those prejudices which contracted views of

nature and _magnified opinions of the experience of man_ may have

begotten.'

[801] Playfair (_Life of Hutton_, p. 64) says that it drew 'their

attention' (_i.e._ the attention of 'men of science'), 'very

slowly, so that several years elapsed before any one showed

himself publicly concerned about it, either as an enemy or a

friend.' He adds, as one of the reasons of this, that it contained

'too little detail of facts for a system which involved so much

that was new, and opposite to the opinions generally received.'

[802] The account of these experiments was read before the Royal Society

of Edinburgh in 1805, and is printed in their _Transactions_, vol.

vi. pp. 71-185, Edinb. 1812, 4to. The general result was (pp. 148,

149), 'That a pressure of 52 atmospheres, or 1700 feet of sea, is

capable of forming a limestone in a proper heat; That under 86

atmospheres, answering nearly to 3000 feet, or about half a mile,

a complete marble may be formed; and lastly, That, with a pressure

of 173 atmospheres, or 5700 feet, that is little more than one

mile of sea, the carbonate of lime is made to undergo complete

fusion, and to act powerfully on other earths.' See also p. 160:

'The carbonic acid of limestone cannot be constrained in heat by a

pressure less than that of 1708 feet of sea.' There is a short,

and not very accurate, notice of these instructive experiments in

_Bakewell's Geology_, London, 1838, pp. 249, 250.

[803] As Sir James Hall says, 'The truth of the most doubtful principle

which Dr. Hutton has assumed, has thus been established by direct

experiment.' _Transactions of the Royal Society of Edinburgh_,

vol. vi. p. 175.

[804] See the remarks of Sir James Hall, in _Transactions_, vol. vi.

pp. 74, 75. He observes that Hutton's 'system, however, involves

so many suppositions, apparently in contradiction to common

experience, which meet us on the very threshold, that most men

have hitherto been deterred from an investigation of its

principles, and only a few individuals have justly appreciated its

merits.' ... 'I conceived that the chemical effects ascribed by

him to compression, ought, in the first place, to be

investigated.' ... 'It occurred to me that this principle was

susceptible of being established in a direct manner by experiment,

and _I urged him to make the attempt; but he always rejected this

proposal_, on account of the immensity of the natural agents,

whose operation he supposed to lie far beyond the reach of our

imitation; and he seemed to imagine that any such attempt must

undoubtedly fail, and thus _throw discredit on opinions, already

sufficiently established, as he conceived, on other principles_.'

I have now given an account of all the most important discoveries made by

Scotland, in the eighteenth century, respecting the laws of the inorganic

world. I have said nothing of Watt, because, although the steam-engine,

which we owe to him, is of incalculable importance, it is not a

discovery, but an invention. An invention it may justly be termed, rather

than an improvement.[805] Notwithstanding what had been effected in the

seventeenth century, by De Caus, Worcester, Papin, and Savery, and

notwithstanding the later additions of Newcomen and others, the real

originality of Watt is unimpeachable. His engine was, essentially, a new

invention; but, under its scientific aspect, it was merely a skilful

adaptation of laws previously known; and one of its most important

points, namely, the economy of heat, was a practical application of ideas

promulgated by Black.[806] The only discovery made by Watt, was that of

the composition of water. Though his claims are disputed by the friends

of Cavendish, it would appear that he was the first who ascertained that

water, instead of being an element, is a compound of two gases.[807] This

discovery was a considerable step in the history of chemical analysis,

but it neither involved nor suggested any new law of nature, and has,

therefore, no claim to mark an epoch in the history of the human

mind.[808] There is, however, one circumstance connected with it which is

too characteristic to be passed over in silence. The discovery was made

in 1783, by Watt, the Scotchman, and by Cavendish, the Englishman,

neither of whom seems to have been aware of what the other was

doing.[809] But between the two there was this difference. Watt, for

several years previously, had been speculating on the subject of water in

connexion with air, and having, by Black's law of latent heat, associated

them together, he was prepared to believe that one is convertible into

the other.[810] The idea of an intimate analogy between the two bodies

having once entered his mind, gradually ripened; and when he, at last,

completed the discovery, it was merely by reasoning from data which

others possessed besides himself. Instead of bringing to light new facts,

he drew new conclusions from former ideas.[811] Cavendish, on the other

hand, obtained his result by the method natural to an Englishman. He did

not venture to draw a fresh inference, until he had first ascertained

some fresh facts. Indeed, his discovery was so completely an induction

from his own experiments, that he omitted to take into consideration the

theory of latent heat, from which Watt had reasoned, and where that

eminent Scotchman had found the premisses of his argument.[812] Both of

these great inquirers arrived at truth, but each accomplished his journey

by a different path. And this antithesis is accurately expressed by one

of the most celebrated of living chemists, who, in his remarks on the

composition of water, truly says, that while Cavendish established the

facts, Watt established the idea.[813]

[805] It may be traced back, certainly to the beginning of the

seventeenth century, and probably still higher. Yet the popular

opinion seems to be correct, that Watt was its real inventor;

though, of course, he could not have done what he did, without his

predecessors. This, however, may be said of all the most eminent

and successful men, as well as of the most ordinary men.

[806] On the obligations of Watt to Black, compare _Brougham's Life of

Watt_ (_Brougham's Works_, vol. i. pp. 25, 36-38, edit. Glasgow,

1855), with _Muirhead's Life of Watt_, second edit. London, 1859,

pp. 66, 83. At p. 301, Mr. Muirhead says of Watt, that 'his

principal inventions connected with the steam-engine, with all

their prodigious results, were founded, as we have seen, on the

attentive observation of great philosophical truths; and the

economy of fuel, increase of productive power, and saving of

animal labour, which gradually ensued, all originated in the

sagacious and careful thought with which he investigated the

nature and properties of heat.' But whatever investigations Watt

made into heat, he discovered no new law respecting it, or, at all

events, no new law which is large enough to be noted in the

history of thermotics, considered purely as a science, and apart

from practical application. Mr. Muirhead, in his interesting work

which I have just quoted, has published (pp. 484-486) some remarks

made on the subject by Watt, several years after the death of

Black, which, though perfectly fair and candid, show that Watt had

a rather confused notion of the real difference between an

invention and a discovery.

[807] Mr. Muirhead, in his _Life of Watt_, pp. 301-370, seems to have

put the priority of Watt beyond further doubt; though he is

somewhat hard upon Cavendish, who, there can be little question,

made the discovery for himself.

[808] I would not wish to diminish one jot of the veneration in which

the great name of Watt is justly held. But when I find the opinion

of Dr. Withering, the botanist, quoted, to the effect that his

'abilities and acquirements placed him next, if not superior, to

Newton.' (_Muirhead's Life of Watt_, p. 302), I cannot but protest

against such indiscriminate eulogy, which would rank Watt in the

same class as one of those godlike intellects of which the whole

world has not produced a score, and which are entitled to be

termed inspired, if ever human being was so. Another instance of

this injudicious panegyric will be found in the same otherwise

excellent work (_Muirhead_, pp. 324, 325), where we read that

Watt's discovery that water consists of oxygen and hydrogen, was

'the commencement of a new era, the dawn of a new day in physical

inquiry, the real foundation of the new system of chemistry; nay,

even a discovery "perhaps of greater importance than any single

fact which human ingenuity has ascertained either before or

since."'

[809] That there was no plagiarism on the part of Watt, we know from

positive evidence; that there was none on the part of Cavendish,

may be fairly presumed, both from the character of the man, and

also from the fact that in the then state of chemical knowledge

the discovery was imminent, and could not have been long delayed.

It was antecedently probable that the composition of water would

be ascertained by different persons at the same time, as we have

seen in many other discoveries which have been simultaneously

made, when the human mind, in that particular department of

inquiry, had reached a certain point. We are too apt to suspect

philosophers of stealing from each other, what their own abilities

are sufficient to work out for themselves. It is, however, certain

that Watt thought himself ill-treated by Cavendish. See _Watt's

Correspondence on the Composition of Water_, London, 1846,

pp. 48, 61.

[810] On 26th November 1783, he writes: 'For many years I have

entertained an opinion that air was a modification of water; which

was originally founded on the facts, that in most cases where air

was actually made, which should be distinguished from those

wherein it is only extricated from substances containing it in

their pores, or otherwise united to them in the state of air, the

substances were such as were known to contain water as one of

their constituent parts, yet no water was obtained in the

processes, except what was known to be only loosely connected with

them, such as the water of the crystallization of salts. _This

opinion arose from a discovery that the latent heat contained in

steam diminished, in proportion as the sensible heat of the water

from which it was produced, increased_; or, in other words, that

the latent heat of steam was less when it was produced under a

greater pressure, or in a more dense state, and greater when it

was produced under a less pressure, or in a less dense state;

which led me to conclude, that when a very great degree of heat

was necessary for the production of the steam, the latent heat

would be wholly changed into sensible heat; and that, in such

cases, the steam itself might suffer some remarkable change. I now

abandon this opinion, in so far as relates to the change of water

into air, as I think that may be accounted for on better

principles.' See this remarkable passage, which is quite decisive

as to the real history of Watt's discovery, in _Correspondence of

James Watt on the Composition of Water_, London, 1846, pp. 84, 85.

Compare p. cxxiv. and p. 248 note.

[811] In the paper which he communicated to the Royal Society, announcing

his discovery, he, well knowing the empirical character of the

English mind, apologizes for this; and says, 'I feel much

reluctance to lay my thoughts on these subjects before the public

in their present indigested state, and _without having been able

to bring them to the test of such experiments as would confirm or

refute them_.' _Watt's Correspondence on the Discovery of the

Composition of Water_, pp. 77, 78. Eleven months earlier, that is

in December 1782, he writes (_Ibid._ p. 4): 'Dr. Priestley has

made a most surprising discovery, which _seems to confirm my

theory_ of water's undergoing some very remarkable change at the

point where all its latent heat would be changed into sensible

heat.'

[812] 'He' (_i.e._ Cavendish) 'here omits entirely the consideration of

latent heat; an omission which he even attempts to justify, in one

of the passages interpolated by Blagden. But it is well known to

every one acquainted with the first principles of chemical

science, even as it was taught in the days of Black, and it was

indisputably familiar to Mr. Watt, that no aëriform fluid can be

converted into a liquid, nor any liquid into a solid, without tho

evolution of heat, previously latent. This essential part of the

process, Mr. Cavendish's theory does not embrace; but without it,

no theory on the subject can be complete; and it will presently be

seen, that Mr. Watt took it fully into account.' _Muirhead's Life

of Watt_, p. 315.

[813] 'Cavendish and Watt both discovered the composition of water.

Cavendish established the facts; Watt the idea.' ... '_The

attaching too high a value to the mere facts, is often a sign of a

want of ideas._' _Liebig's Letters on Chemistry_, London, 1851, p.

48. The last sentence of this illustrious philosopher, which I

have put in italics, should be well pondered in England. If I had

my way, it should be engraved in letters of gold over the portals

of the Royal Society and of the Royal Institution.

Thus much, as to what was effected by the Scotch in the department of

inorganic science. If we now turn to organic science, we shall find that,

there also, their labours were very remarkable. To those who are capable

of a certain elevation and compass of thought, it will appear, in the

highest degree, probable, that, between the organic and inorganic world,

there is no real difference. That they are separated, as is commonly

asserted, by a sharp line of demarcation, which indicates where one

abruptly ends, and the other abruptly begins, seems to be a supposition

altogether untenable. Nature does not pause, and break off in this fitful

and irregular manner. In her works there is neither gap nor chasm. To a

really scientific mind, the material world presents one vast and

uninterrupted series, gradually rising from the lowest to the highest

forms, but never stopping. In one part of that series, we find a

particular structure, which, so far as our observations have yet

extended, we, in another part, cannot find. We also observe particular

functions, which correspond to the structure, and, as we believe, result

from it. This is all we know. Yet, from these scanty facts, we, who, at

present, are still in the infancy of knowledge, and have but skimmed the

surface of things, are expected to infer, that there must be a point, in

the chain of existence, where both structure and function suddenly cease,

and, after which, we may vainly search for signs of life. It would be

difficult to conceive a conclusion more repugnant to the whole march and

analogy of modern thought. In every department, the speculations of the

greatest thinkers are constantly tending to coördinate all phenomena, and

to regard them as different, indeed, in degree, but by no means as

different in kind. Formerly, men were content to ground their conviction

of this difference in kind, on the evidence of the eye, which, on a

cursory inspection, saw an organization in some bodies, and not in

others. From the organization, they inferred the life, and supposed that

plants, for instance, had life, but that minerals had none. This sort of

argument was long deemed satisfactory; but, in the course of time, it

broke down; more evidence was required, and, since the middle of the

seventeenth century, it has been universally admitted, that the eye, by

itself, is an untrustworthy witness, and that we must employ the

microscope, instead of relying on the unaided testimony of our own puny

and precarious senses. But the microscope is steadily improving, and we

cannot tell what limits there are to its capacity for improvement.

Consequently, we cannot tell what fresh secrets it may disclose. Neither

can we say, that it may not be altogether superseded by some new

artificial resource, which shall furnish us with evidence, as superior to

any yet supplied, as our present evidence is superior to that of the

naked eye. Even already, and notwithstanding the shortness of time during

which the microscope has been a really effective instrument, it has

revealed to us organizations, the existence of which no one had

previously suspected. It has proved, that what, for thousands of years,

had been deemed mere specks of inert matter, are, in truth, animals

possessing most of the functions which we possess, reproducing their

species in regular and orderly succession, and endowed with a nervous

system, which shows that they must be susceptible of pain and enjoyment.

It has detected life hidden in the glaciers of Switzerland; it has found

it embedded in the polar ice, and, if it can flourish there, it is hard

to say from what quarter it can be shut out. So unwilling, however, are

most men to relinquish old notions, that the resources of chemistry have

been called in, to ascertain the supposed difference between organic and

inorganic matter: it being asserted, that, in the organic world, there is

a greater complexity of molecular combination, than in the

inorganic.[814] Chemists further assert, that, in organic nature, there

is a predominance of carbon, and, in inorganic, a predominance of

silicon.[815] But chemical analysis, like microscopic observation, is

making such rapid strides, that each generation, I had almost said each

year, is unsettling some of the conclusions previously established; so

that, now, and for a long time hence, we must regard those conclusions as

empirical, and, indeed, as merely tentative. Surely a permanent and

universal inference cannot be drawn from shifting and precarious facts,

which are admitted to-day, and may be overthrown to-morrow. It would,

therefore, appear that, in favour of the opinion, that some bodies are

living, and that others are dead, we have nothing, except the

circumstance, that our researches, so far as they have yet gone, have

shown that cellular structure, growth, and reproduction, are not the

invariable properties of matter, but are excluded from a large part of

the visible world, which, on that account, we call inanimate. This is the

whole of the argument on that side of the question. On the other side, we

have the fact, that our sight, and the artificial instruments, by whose

aid we have arrived at this conclusion, are confessedly imperfect; and we

have the further fact, that, imperfect as they are, they have proved,

that the organic kingdom is infinitely more extensive than the boldest

dreamer had ever imagined, while they have not been able to enlarge the

boundaries of the inorganic kingdom to any thing like the same amount.

This shows, that, so far as our opinions are concerned, the balance is

steadily inclining in one given direction; in other words, as our

knowledge advances, a belief in the organic is encroaching upon a belief

in the inorganic.[816] When we, moreover, add, that all science is

manifestly converging towards one simple and general theory, which shall

cover the whole range of material phenomena, and that, at each successive

step, some irregularities are explained away, and some inequalities are

reduced, it can hardly be doubted, that such a movement tends to weaken

those old distinctions, the reality of which has been too hastily

assumed; and that, in their place, we must, sooner or later, substitute

the more comprehensive view, that life is a property of all matter, and

that the classification of bodies into animate and inanimate, or into

organic and inorganic, is merely a provisional arrangement, convenient,

perhaps, for our present purposes, but which, like all similar divisions,

will eventually be merged in a higher and wider scheme.

[814] 'Organic substances, whether directly derived from the vegetable

or animal kingdom, or produced by the subsequent modification of

bodies which thus originate, are remarkable as a class for a

degree of complexity of constitution far exceeding that observed

in any of the compounds yet described.' _Fownes' Chemistry_, 3rd

edit., London, 1850, p. 353. I quote this, as the first authority

at hand, for a doctrine which is universally admitted by chemists,

and which is indubitably true, _so far as our experiments have at

present extended_.

[815] 'As the organic world is characterized by the predominance, in

quantity, of carbon, so the mineral or inorganic world is marked

by a similar predominance of silicon.' _Turner's Chemistry_,

edited by Liebig and Gregory, vol. ii. p. 678, London, 1847.

[816] I mean, of course, to apply this remark only to the globe we

inhabit, and not to extra-terrestrial phenomena. Respecting the

organization or non-organization of what exists out of this earth,

we have no evidence, and can hardly expect to have any for

centuries. Inferences have, indeed, been drawn from telescopic

observations; and attempts are now being made, abroad, to

determine, by a still more refined process, the physical

composition of some of the heavenly bodies. But without venturing,

in this note, to enter into such discussions, or even to state

their purport, I may say, that the difficulty of _verification_

will long prove an insuperable barrier to our knowledge of the

truth or falsehood of any results which may be obtained.

Until, however, that step is taken, we must be content to reason

according to the evidence supplied by our imperfect instruments, or by

our still more imperfect senses. We, therefore, recognize the difference

between organic and inorganic nature, not as a scientific truth, but as a

scientific artifice, by which we separate in idea, what is inseparable in

fact; hoping, in this way, to pursue our course with the greater ease,

and ultimately to obtain results, which will make the artifice needless.

Assuming, then, this division, we may refer all investigations of organic

bodies to one of two objects. The first object is, to ascertain the law

of those bodies, in their usual, healthy, or, as we somewhat erroneously

phrase it, normal course. The other object is, to ascertain their law, in

their unusual, unhealthy, or abnormal course. When we attempt to do the

first of these things, we are physiologists. When we attempt to do the

second, we are pathologists.[817]

[817] Mr. Simon, in his thoughtful and suggestive Lectures, says, 'We

may describe Pathology to consist in the Science of Life under

other conditions than those of ideal perfection.' _Simon's

Lectures on Pathology_, London, 1850, p. 14. This is by far the

best description I have met with; though, as it involves a

negative, it cannot be accepted as a definition. Indeed, the

context shows that Mr. Simon does not suppose it to be one.

Physiology and pathology are thus the two fundamental divisions of all

organic science.[818] Each is intimately connected with the other; and

eventually, no doubt, both will be fused into a single study, by

discovering laws which will prove that here, as elsewhere, nothing is

really abnormal, or irregular. Hitherto, however, the physiologists have

immeasurably outstripped the pathologists in the comprehensiveness of

their views, and, therefore, in the value of their results. For, the

best physiologists distinctly recognize that the basis of their science

must include, not only the animals below man, but also the entire

vegetable kingdom, and that, without this commanding survey of the whole

realm of organic nature, we cannot possibly understand even human

physiology, still less general physiology. The pathologists, on the other

hand, are so much in arrear, that the diseases of the lower animals

rarely form part of their plan; while the diseases of plants are almost

entirely neglected, although it is certain that, until all these have

been studied, and some steps taken to generalize them, every pathological

conclusion will be eminently empirical, on account of the narrowness of

the field from which it is collected.

[818] I formerly adopted the commonly received division of organic

statics, and organic dynamics; the statics being anatomy, and the

dynamics being physiology. But, I now think that our knowledge is

not sufficiently advanced to make this so convenient as the

division into physiological and pathological, or into normal and

abnormal, provided we remember that in reality nothing is

abnormal. The practically useful, but eminently unscientific,

doctrine, that there can be alteration of function without

alteration of structure, has effaced some of the most essential

distinctions between anatomy and physiology, and especially

between morbid anatomy and morbid physiology. Until those

distinctions are recognized, the scientific conceptions of

professional writers must be confused, however valuable their

practical suggestions may be. While men are capable of believing

that it is _possible_ for variations of function to proceed from

any cause except variations of structure, the philosophic

importance of anatomy will be imperfectly appreciated, and its

true relation to physiology will remain undefined. Inasmuch,

however, as, with our actual resources, the most careful

dissection is often unable to detect (in insanity, for instance)

those changes of structure which produce changes of function,

superficial thinkers are placed under a strong temptation to deny

their invariable connexion; and while the microscope is so

imperfect, and chemistry so backward, it is impossible that

experiments should always convince them of their mistake. Hence, I

believe that until our means of empirical research are greatly

improved, all such investigations, notwithstanding their immense

value in other respects, will tend to lead mere inductive minds

into error, by making them rely too much on what they call the

facts of the case, to the prejudice of the reason. This is what I

mean by saying, that our knowledge is not sufficiently advanced to

make it advisable to divide the sciences of organic bodies into

physiological and anatomical. At present, and probably for some

time yet, the humbler division into physiological and

pathological, may be deemed safer, and more likely to produce

solid results.

The science of pathology being still so backward in the conception as

well as in the execution, that even men of real ability believe that it

can be raised from a mere study of the human frame, it will hardly be

expected that the Scotch, notwithstanding the marvellous boldness of

their speculations, should have been able, in the eighteenth century, to

anticipate a method which the nineteenth century has yet to employ. But

they produced two pathologists of great ability, and to whom we owe

considerable obligations. These were, Cullen and John Hunter.[819] Cullen

was eminent only as a pathologist; but Hunter, whose fine and discursive

genius took a much wider range, was great both in physiology and in

pathology. A short account of their generalizations respecting organic

science, will be a fitting sequel to the notices I have already given of

what was done by their countrymen for inorganic science, during the same

period. It will complete our survey of the Scotch intellect, and will

enable the reader to form some idea of the brilliant achievements of that

most remarkable people, who, contrary to the course of affairs in all

other modern nations, have shown that scientific discoveries do not

necessarily weaken superstition, and that it is possible for two hostile

principles to flourish side by side, without ever coming into actual

collision, or without sensibly impairing each other's vigour.

[819] Hunter, as we shall presently see, did take an extraordinarily

comprehensive view of pathology, including the whole of the

organic world and even the aberrations of form in the inorganic.

In 1751, Cullen was appointed professor of medicine in the University of

Glasgow;[820] from which, however, in 1756, he was removed to the

University of Edinburgh,[821] where he delivered those celebrated

lectures, on which his fame now depends. During the early part of his

career, he paid great attention to inorganic physics, and propounded some

remarkable speculations, which are supposed to have suggested the theory

of latent heat to Black, who was his pupil.[822] But, to follow out those

views, would have required a number of minute experiments, which it did

not suit the habit of his mind to make. Having, therefore, put forth his

ideas, he left them to germinate, and passed on to his arduous attempt to

generalize the laws of disease as they are exhibited in the human frame.

In the study of disease, the phenomena being more obscure and less

amenable to experiment, there was greater latitude for speculation;

hence, he could more easily indulge in that love of theory, which was his

ruling passion, and with an extreme devotion to which he has been

reproached.[823] That the reproach is not altogether unjust, must, I

think, be admitted, since we find him laying down the doctrine, that,

inasmuch as, in the treatment of disease, theory could not be separated

from practice, it was unimportant which came first.[824] This was

tantamount to saying, that a medical practitioner might allow his

theories to control his observations; for it is certain that, in an

immense majority of cases, men are so tenacious of the opinions they

imbibe, that whatever, in any pursuit, first occupies their

understanding, is likely to mould all that comes afterwards. In ordinary

minds, associations of ideas, if firmly established, become indissoluble;

and the power of separating them, and of arranging them in new

combinations, is one of the rarest of our endowments. An average

intellect, when once possessed by a theory, can hardly ever escape from

it. Hence, in practical matters, theory should be feared, just as, in

scientific matters, it should be cherished; because practical pursuits

are chiefly engrossed by the lower class of minds, where associations and

the force of prejudice are extremely strong, while scientific pursuits

concern the higher class, where such prepossessions are comparatively

weak, and where close associations are more easily severed. The most

powerful intellects are most accustomed to new arrangements of thought,

and are, therefore, most able to break up old ones. On them, belief sits

lightly, because they well know how little evidence we have for many of

even our oldest beliefs. But the average, or, as we must say, without

meaning offence, the inferior, minds, are not disturbed by these

refinements. Theories, which they have once heartily embraced, they can

hardly ever get rid of, and they often dignify them with the name of

essential truths, and resent every attack upon them as a personal injury.

Having inherited such theories from their fathers, they regard them with

a sort of filial piety, and cling to them as if they were some rich

acquisition, which no one has a right to touch.

[820] _Thomson's Life of Cullen_, vol. i. p. 70, Edinburgh, 1832.

[821] _Thomson's Life of Cullen_, vol. i. p. 96. Bower states that

Cullen 'was appointed to the chair in 1755.' _Bower's History of

the University of Edinburgh_, vol. ii. p. 216, Edinburgh, 1817.

[822] 'It seems impossible to peruse the passages I have quoted from

Dr. Cullen's manuscript lectures and papers, and from his Essay on

Evaporation, without perceiving that his investigations with

regard to the heat and cold occasioned by the combination,

liquefaction, and evaporation of bodies, must not only have

assisted to direct the attention of his pupil Dr. Black to similar

inquiries, but must also have furnished him with several of the

data from which his simple and comprehensive theory of Latent Heat

was afterwards so philosophically deduced.' _Thomson's Life of

Cullen_, vol. i. p. 56.

[823] 'It is allowed by the admirers of this great man, that he was

perhaps too fond of theory.' _Bower's History of the University of

Edinburgh_, vol. iii. p. 273

[824] In 1759, he wrote to Dr. Balfour Russell, one of his favourite

pupils: 'You will not find it possible to separate practice from

theory altogether; and therefore, if you have a mind to begin with

the theory, I have no objection.' _Thomson's Life of Cullen_, vol.

i. p. 130. Compare his _Introductory Lectures to the Practice of

Physic_, where, asserting truly, 'that reasoning in physic is

unavoidable' (_Cullen's Works_, vol. i. p. 417), he boldly infers,

'that to render it safe, it is _necessary to cultivate theory in

its full extent_.'

To this latter class, nearly all men belong, who are more engaged in

practical pursuits than in speculative ones. Among them, are the ordinary

practitioners, whether in medicine or in any other department, extremely

few of whom are willing to break up trains of thought to which they are

inured.[825] Though they profess to despise theory, they are, in reality,

enslaved by it. All that they can do, is to conceal their subjection, by

terming their theory a necessary belief. It must, therefore, be deemed a

remarkable proof of Cullen's love of deductive reasoning, that he,

sagacious and clear-sighted as he was, should have supposed that, in so

practical an art as medicine, theory could, with impunity, precede

practice. For, it is most assuredly true, that, taking men in the

average, their minds are so constructed, that it cannot precede it

without controlling it. It is equally true, that such control must be

hurtful. Even now, and notwithstanding the great steps which have been

taken in morbid anatomy, in animal chemistry, and in the microscopic

investigation both of the fluids and solids of the human frame, the

treatment of disease is a question of art, far more than a question of

science. What chiefly characterizes the most eminent physicians, and

gives them their real superiority, is not so much the extent of their

theoretical knowledge,--though that, too, is often considerable,--but it

is that fine and delicate perception which they owe, partly to

experience, and partly to a natural quickness in detecting analogies and

differences which escape ordinary observers. The process which they

follow, is one of rapid, and, in some degree, unconscious, induction. And

this is the reason why the greatest physiologists and chemists, which the

medical profession possesses, are not, as a matter of course, the best

curers of disease. If medicine were a science, they would always be the

best. But medicine, being still essentially an art, depends mainly upon

qualities which each practitioner has to acquire for himself, and which

no scientific theory can teach. The time for a general theory has not yet

come, and probably many generations will have to elapse before it does

come. To suppose, therefore, that a theory of disease should, as a matter

of education, precede the treatment of disease, is not only practically

dangerous, but logically false. With its practical danger I am not now

concerned; but its logical aspect is a curious illustration of that

passion for systematic and dialectic reasoning which characterized

Scotland. It shows that Cullen, in his eagerness to argue from principles

to facts, instead of from facts to principles, could, in the most

important of all arts, recommend a method of procedure, for which even

our knowledge is not ripe, but which, in his time, was so singularly rash

and immature, that nothing can explain its adoption by a man of such

vigorous understanding, except the circumstance of his living in a

country in which that peculiar method reigned supreme.

[825] Even Cullen himself says, rather roughly, 'The great horde of

physicians are always servile imitators, who can neither perceive

nor correct the faults of their system, and are always ready to

growl at, and even to worry, the ingenious person that could

attempt it. Thus was the system of Galen secured in the possession

of the schools of physic, till soon after the irruption of the

Goths and Vandals destroyed every vestige of literature in the

western parts of Europe, and drove all that remained of it to seek

a feeble protection at Constantinople.' _Lectures Introductory to

the Practice of Physic_, in _Cullen's Works_, vol. i. p. 386,

Edinburgh, 1827.

It must, however, be admitted that Cullen wielded the method with great

ability, especially in his application of it to the science of pathology,

to which it was far better suited than to the art of therapeutics. For,

we must always remember, that the science which investigates the laws of

disease, is quite a different thing from the art which cures it. The

science has a speculative interest, which is irrespective of all

practical considerations, and which depends simply on the fact, that,

when it is completed, it will explain the aberrations of the whole

organic world. Pathology aims at ascertaining the causes which determine

every departure from the natural type, whether of form or of function.

Hence it is, that no one can take a comprehensive view of the actual

state of knowledge, without studying the theoretic relations between

pathology and other departments of inquiry. To do this, is the business,

not of practical men, but of philosophers, properly so called. The

philosophic pathologist is as different from the physician, as a jurist

is different from an advocate, or as an agricultural chemist is different

from a farmer, or as a political economist is different from a statesman,

or as an astronomer, who generalizes the laws of the heavenly bodies, is

different from a captain, who navigates his ship by a practical

application of those laws. The two sets of functions may be united, and

occasionally, though very rarely, they are, but there is no necessity for

their being so. While, therefore, it would be absurdly presumptuous for

an unprofessional person to pass judgment on the therapeutical system of

Cullen, it is perfectly legitimate for any one, who has studied the

theory of these matters, to examine his pathological system; because

that, like all scientific systems, must be amenable to general

considerations, which are to be taken, partly from the adjoining

sciences, and partly from the universal logic of philosophic method.

It is from this latter, or logical, point of view, that Cullen's

pathology is interesting for the purposes of the present chapter. The

character of his investigations may be illustrated by saying, that his

method in pathology is analogous to that which Adam Smith adopted at the

same time, though in a very different field. Both were deductive; and

both, before arguing deductively, suppressed some of the premisses from

which they reasoned. That this suppression is the key to Adam Smith's

method, and was an intentional part of his plan, I have already shown; as

also that, in each of his two works, he supplied the premisses in which

the other work was deficient. In this respect, he was far superior to

Cullen. For, though Cullen, like Smith, began by mutilating his problem

in order to solve it more readily, he, unlike Smith, did not see the

necessity of instituting another and parallel inquiry, which should

complete the scheme, by starting from the premisses that had been

previously omitted.

What I have termed the mutilation of the problem, was effected by Cullen

in the following manner. His object was, to generalize the phenomena of

disease, as they are exhibited in the human frame; and it was obvious to

him, as to every one else, that the human frame consists partly of solids

and partly of fluids. The peculiarity of his pathology is, that he

reasons almost entirely from the laws of the solids, and makes so little

account of the fluids, that he will only allow them to be the indirect

causes of disease, which, in a scientific view, are to be deemed strictly

subordinate to the direct causes, as represented by the solid

constituents of our body.[826] This assumption, though false, was

perfectly justifiable, since, by curtailing the problem, he simplified

its study; just as Adam Smith, in his _Wealth of Nations_, simplified the

study of human nature, by curtailing it of all its sympathy. But this

most comprehensive thinker was careful, in his _Theory of Moral

Sentiments_, to restore to human nature the quality of which the _Wealth

of Nations_ had deprived it; and, by thus establishing two different

lines of argument, he embraced the whole subject. In the same way, it was

incumbent on Cullen, after having constructed a theory of disease by

reasoning from the solids, to have constructed another theory by

reasoning from the fluids; so that a coördination of the two theories

might have raised a science of pathology, as complete as the then state

of knowledge allowed.[827] But to this, his mind was unequal. Able though

he was, he lacked the grasp of intellect which characterized Adam Smith,

and which made that great man perceive, that every deductive argument

which is founded on a suppression of premisses, must be compensated by a

parallel argument, which takes those premisses into account.[828] So

little was Cullen aware of this, that, having built up that system of

pathology which is known to medical writers as Solidism, he never took

the pains to accompany it by another system, which gave the first rank to

the fluids. On the contrary, he believed that his plan was complete and

exhaustive, and that what is termed Humoral Pathology was a fiction,

which had too long usurped the place of truth.[829]

[826] This idea runs through the whole of his writings. In the following

passage, it is more succinctly stated than in any other: 'In

pathology, and in the prognosis of particular diseases, it is

absolutely necessary to enter into the distinction of these

causes. I call the one _direct_ causes, those which act upon the

nervous system directly; and the other _indirect_ causes, those

which produce the same effect, but by destroying those organs

which are necessary to the support of the excitement, viz. the

whole system of circulation.' _Cullen's Works_, vol. i. p. 135.

Even this passage, clear as it seems, can only be rightly

interpreted by taking the context into consideration.

[827] For, as is truly observed by probably the greatest pathologist of

our time, 'Humoral pathology is simply a requirement of common

practical sense; and it has always held a place in medical

science, although the limits of its domain have, no doubt, been

variously circumscribed or interpreted at different times. Of late

years, it has met with a new basis and support in morbid anatomy,

which, in the inadequacy of its discoveries in the solids to

account for disease and death, has been compelled to seek for an

extension of its boundary through a direct examination of the

blood itself.' _Rokitansky's Pathological Anatomy_, vol. i. p.

362, London, 1854.

[828] Unless, as is the case in geometry, the premisses, which are

suppressed, are so slight as to be scarcely perceptible.

[829] He was so indignant at the bare idea of a humoral pathology, that

even Hoffmann, who before himself was the most eminent advocate of

solidism, fell under his displeasure for allowing some little

weight to the humoral doctrines. He says that Hoffmann 'has not

applied his fundamental doctrine so extensively as he might have

done; and he has everywhere intermixed an humoral pathology, as

incorrect and hypothetical as any other.' _Cullen's Works_, vol.

i. p. 410. At p. 470, 'I have, therefore, assumed the general

principles of Hoffmann. And, if I have rendered them more correct,

and more extensive in their application, and, _more particularly,

if I have avoided introducing the many hypothetical doctrines of

the Humoral Pathology which disfigured both his and all the other

systems that have hitherto prevailed_, I hope I shall be excused

for attempting a system, which, upon the whole, may appear new.'

Several of the views advocated by Cullen were taken from Hoffmann, and

several of the facts from Gaubius; but that his pathology, considered as

a whole, is essentially original, is evident from a certain unity of

design which is inconsistent with extensive plagiarism, and which proves

that he had thoroughly thought out his subject for himself. Without,

however, stopping to inquire how much he borrowed from others, I will

briefly indicate a few of the salient points of his system, in order to

enable the reader to understand its general character.

According to Cullen, all the solids in the human body are either simple

or vital. The simple solids retain, after death, the properties which

they possessed during life. But the vital solids, which form the

fundamental part of the nervous system, are marked by properties, which

disappear directly death occurs.[830] Hence, the simple solids, having

fewer functions than the vital, have also fewer diseases; and the

maladies to which they are liable admit of easy classification.[831] The

real difficulty lies in the vital solids, because on their peculiarities

the whole nervous system depends, and nearly all disorders are

immediately due to changes in them. Cullen, therefore, made the nervous

system the basis of his pathology; and, in speculating on its functions,

he assigned the chief place to an occult principle, which he termed the

Animal Power, or Energy, of the brain.[832] This principle acted on the

vital solids. When the principle worked well, the body was healthy; when

it worked ill, the body was unhealthy. Since, then, the state of the

vital solids was the main cause of disorder, and since the Energy of the

brain was the main cause of the state of the vital solids, it became

important to know what the influences were which acted on the Energy,

because in them we should find the beginning of the series. Those

influences were divided by Cullen into physical and mental. The physical

were, heat, cold, and effluvia, the three most potent of the material

disturbers of the human frame.[833] The mental influences, which excited

the brain to act on the solids, were comprised under six different heads,

namely, the will, the emotions, the appetites, the propensities, and,

finally, the two great principles of habit and of imitation, on which he,

with good reason, laid considerable stress.[834] In arguing from these

mental causes, and in generalizing the relations between them and the

sensations of the body, he, faithful to his favourite method, proceeded

deductively from the metaphysical principles then in vogue, without

inquiring inductively into their validity, such an induction being, he

thought, no part of his duty.[835] He was too anxious to get on with his

dialectic, to be interrupted by so trifling a matter as the truth or

falsehood of the premisses on which the reason rested. What he did in the

metaphysical part of his pathology, he also did in its physical part.

Although the blood and the nerves are the two leading features of the

human economy, he did not search into them by a separate induction; he

subjected them neither to chemical experiments in order to learn their

composition, nor to microscopic observations in order to learn their

structure.[836] This is the more observable, because though we must admit

that animal chemistry was then generally neglected, and that its real

meaning was scarcely understood until the wonderful labours of Berzelius

revealed its importance, still the microscope was ready to Cullen's

hands; it having been invented a hundred and fifty years before he

completed his pathology, and having been in common scientific use for

about a hundred years. But his love of synthesis overcame him. His system

is constructed by reasoning from general principles; and of that process,

he certainly was a consummate master. Between the premisses and the

conclusion, he hardly ever lets error creep in. And, in reference to the

results of his speculations, he had one immense merit, which will always

secure to him a conspicuous place in the history of pathology. By

insisting on the importance of the solids, he, one-sided though he was,

corrected the equal one-sidedness of his predecessors; for, with

extremely few exceptions, all the best pathologists, from Galen

downwards, had erred in ascribing too much to the fluids, and had upheld

a purely humoral pathology. Cullen turned the minds of men in the other

direction; and though, in teaching them that the nervous system is the

sole primary seat of disease, he committed a great mistake, it was a

mistake of the most salutary kind. By leaning on that side, he restored

the balance. Hence, I have no doubt, he indirectly encouraged those

minute researches into the nerves, which he would not himself stop to

make, but which, in the next generation, gave rise to the capital

discoveries of Bell, Shaw, Mayo, and Marshall Hall. At the same time, the

old humoral pathology, which had prevailed for many centuries, was

practically pernicious, because, assuming that all diseases are in the

blood, it produced that constant and indiscriminate venesection, which

destroyed innumerable lives, besides the irreparable injury it often

inflicted both on body and mind; weakening those whom it was unable to

slay. Against this merciless onslaught, which made medicine the curse of

mankind, the Solid Pathology was the first effective barrier.[837]

Practically, therefore, as well as speculatively, we must hail Cullen as

a great benefactor of his species; and we must regard his appearance as

an epoch in the history of human comfort, as well as in the history of

human thought.

[830] 'The solid parts of the body seem to be of two kinds: one whose

properties are the same in the dead as in the living, and the same

in the animate as in many inanimate bodies; the other, whose

properties appear only in living bodies. In the last, a peculiar

organization, or addition, is supposed to take place; in

opposition to which the first are called the simple solids. Of

these only, we shall treat here; and of the others, which may be

called vital solids, being the fundamental part of the nervous

system, we shall treat under that title in the following section.'

_Cullen's Works_, vol. i. p. 10.

[831] These diseases are laxity, flaccidity, &c. See the enumeration of

'the diseases of the simple solids,' in _Cullen's Works_, vol. i.

p. 14.

[832] _Cullen's Works_, vol. i. pp. 65, 600, vol. ii. p. 364.

Dr. Thomson, who had access to papers and lectures of Cullen's,

which have never been published, says (_Life of Cullen_, vol. i.

p. 265), 'His speculations with regard to the different functions

of the nervous system, but more particularly with regard to that

of the Animal Power or Energy of the brain, were incorporated with

every opinion which he taught concerning the phenomena of the

animal economy, the causes of diseases, and the operation of

medicines; and they may be said to constitute a most important

part, if not the sole basis, of that system of the Practice of

Physic, which he made the subject of prelection, as well as of

study, for a period of nearly forty years, before he ventured to

give it to the public.' I should mention, that Cullen, under the

term 'brain,' included the contents of the vertebral column as

well as of the cranium.

[833] _Cullen's Works_, vol. i. pp. 40, 546, 558, 648, vol. ii. p. 321.

[834] _Cullen's Works_, vol. i. pp. 86, 91, 100, 101, 108, 115, 116,

553, 592, vol. ii. pp. 35, 366. Compare the summary of causes in

_Thomson's Life of Cullen_, vol. i. p. 289.

[835] He says (_Works_, vol. i. pp. 31, 32), 'Whoever has the smallest

tincture of metaphysics will know the distinction pointed at here

between the qualities of bodies as primary and secondary.' ...

'_Whether these distinctions be well or ill founded, it is not my

business to inquire._' But though he did not deem it his business

to inquire into the accuracy of these and similar distinctions, he

thought himself justified in assuming them, and reasoning from

them as if they could explain the working of those sensations,

whose perversion formed the point of contact between metaphysics

and pathology. See, for instance, in his _Works_, vol. i. p. 46,

the long series of unproved and improvable assertions respecting

the combination and comparison of sensations giving rise to

memory, imagination, and the like.

[836] Cullen, with that admirable candour which was one of the most

attractive peculiarities of his fine intellect, confesses his want

of acquaintance with the microscope: 'It leaves me, who am not

conversant in such observations, altogether uncertain with respect

to the precise nature of this part of the blood.' _Cullen's

Works_, vol. i. p. 195. A pathologist without a microscope is an

unarmed man, indeed. In regard to his animal chemistry, one

passage may be quoted as a specimen of the manner in which he

arrived at conclusions speculatively, instead of subjecting the

phenomena to experimental investigation. 'We may remark it to be

highly probable, that all animal matter is originally formed of

vegetable; because all animals either feed directly and entirely

on vegetables, or upon other animals that do so. From hence it is

probable, that all animal substances may be traced to a vegetable

origin; and _therefore_, if we would inquire into the production

of animal matter, we _must first inquire_ in what manner vegetable

matter may be converted into animal?' _Cullen's Works_, vol. i.

pp. 177, 178. The _therefore_ and the _must_, resulting merely

from an antecedent probability, are characteristic of that

over-boldness, into which deduction is apt to degenerate, and

which is strongly contrasted with the opposite vice of

over-timidity, by which inductive reasoners are tainted.

[837] Dr. Watson (_Principles and Practice of Physic_, 4th edit. London,

1857, vol. i. p. 41) says of the humoral pathology, that, 'the

absurdity of the hypothesis, and _still more the dangerous

practice which this doctrine generated_, began to be manifest, and

led to its total abandonment.' But, with every respect for this

eminent authority, I venture to observe, that this supposition of

Dr. Watson's is contradicted by the whole history of the human

mind. There is no well-attested case on record of any theory

having been abandoned, because it produced dangerous results. As

long as a theory is believed, men will ascribe its evil

consequences to any cause except the right one. And a theory which

is once established, will always be believed, until there is some

change in knowledge which shakes its foundation. Every practical

change may, by careful analysis, be shown to depend, in the first

instance, on some change of speculative opinions. Even at the

present day, many doctrines are generally held in the most

civilized countries, which are producing dangerous practical

consequences, and have produced those consequences for centuries.

But the mischief which the doctrine engenders does not weaken the

doctrine itself. Nothing can do that, but the general progress of

knowledge, which, by altering former opinions, modifies future

conduct.

It may, perhaps, facilitate the conceptions of unprofessional readers, if

I give, in as few words as possible, a specimen of the way in which

Cullen employed his method, in investigating the theory of some one class

of diseases. For this purpose, I will select his doctrine of fever,

which, though now generally abandoned, once exercised more influence than

any other part of his pathology. Here, as elsewhere, he reasons from the

solids.[838] Disregarding the state of the blood, he says, that the cause

of all fever is a diminished energy of the brain.[839] Such diminution

may be produced by various sedatives, the most common of which are

effluvia, whether marsh or human, intemperance, fear, and cold.[840]

Directly the energy of the brain is impaired, the disease begins. Rapidly

passing through the nervous system, its first palpable effect is a chill,

or cold fit, which is accompanied by a spasm on the extremities of the

arteries, particularly where they touch the surface of the body.[841]

This spasm on the extreme vessels, irritates the heart and arteries, and

the irritation continues till the spasm is relaxed.[842] At the same

time, the increased action of the heart restores the energy of the brain;

the system rallies; the extreme vessels are relieved; while, as a

consequence of the whole movement, sweat is excreted, and the fever

abates.[843] Shutting out, therefore, all consideration of the fluids of

the body, the successive stages of languor, cold fit, and hot fit, might,

in Cullen's opinion, be generalized by reasoning merely from the solids,

which, furthermore, produced his well-known distinction between fevers,

the continuance of which is owing to an excess of spasm, and those, the

continuance of which is owing to an excess of debility.[844]

[838] Some writers, who have taken notice of Cullen, have been deceived

in this respect by his occasional use of the expression 'nervous

fluid,' as if he were willing to let in the idea of humorism. But,

in one place, he distinctly guards himself against such

misconstruction. 'Now, to avoid determining any thing with regard

to these opinions, I have used the term of _nervous power_; but as

this is a little ambiguous, I choose to express it by _nervous

fluid_; not that I suppose, with Dr. Boerhaave, that the brain is

an excretory, and that a fluid is secreted from it: _I mean

nothing more than that there is a condition of the nerves which

fits them for the communication of motion_. But I defer the

consideration of these opinions for the present, and perhaps _ad

Græcas calendas_; but nothing shall be rested upon the nervous

fluid, it shall be considered merely as _a power_ fitted for

communicating motions.' _Cullen's Works_, vol. i. p. 17. Without

this passage, his remarks on 'the nervous fluid in the brain'

(_Works_, vol. i. p. 129), might easily be misunderstood.

[839] 'Together with this, the languor, inactivity, and debility of the

animal motions, the imperfect sensations, the feeling of cold,

while the body is truly warm, and some other symptoms, all show

that the energy of the brain is, on this occasion, greatly

weakened; and I presume that, as the weakness of the action of the

heart can hardly be imputed to any other cause, this weakness also

is a proof of the diminished energy of the brain. So I conclude,

that a debility of the nervous power forms the beginning of the

cold fit, and lays the foundation of all the other phenomena.'

_Practice of Physic_, in _Cullen's Works_, vol. i. p. 492.

[840] 'To render our doctrine of fever consistent and complete, it is

necessary to add here, that these remote causes of fever, human

and marsh effluvia, seem to be of a debilitating or sedative

quality.' ... 'Though we have endeavoured to show that fevers

generally arise from marsh or human effluvia, we cannot, with any

certainty, exclude some other remote causes, which are commonly

supposed to have at least a share in producing those diseases. And

I proceed, therefore, to inquire concerning these causes; the

first of which that merits attention, is the power of cold applied

to the human body.' ... 'Besides cold, there are other powers that

seem to be remote causes of fever; such as fear, intemperance in

drinking, excess in venery, and other circumstances, which

evidently weaken the system. But whether any of these sedative

powers be alone the remote cause of fever, or if they only operate

either as concurring with the operation of marsh or human

effluvia, or as giving an opportunity to the operation of cold,

are questions not to be positively answered.' _Practice of

Physic_, in _Cullen's Works_, vol. i. pp. 546, 552. One part of

this view has been corroborated, since the time of Cullen. 'The

experiments of Chossat and others clearly prove cold to be a

direct sedative.' _Williams' Principles of Medicine_, 2nd edit.

London, 1848, p. 11. Compare _Watson's Principles and Practice of

Physic_, 4th edit. London, 1857, vol. i. pp. 87-92, 249. Hence,

perhaps, the 'irresistible tendency to sleep caused by exposure to

severe or long-continued cold.' _Erichsen's Surgery_, 2nd edit.

London, 1857, p. 336; but as to this, Dr. Watson (_Principles of

Physic_, vol. i. p. 89) is sceptical, and thinks that, in those

cases which are recorded, the drowsiness ascribed to cold, is, in

a great measure, the result of fatigue.

[841] _Cullen's Works_, vol. i. p. 493. Compare, respecting his general

theory of spasm, p. 84, and vol. ii. p. 400.

[842] 'The idea of fever, then, may be, that a spasm of the extreme

vessels, however induced, proves an irritation to the heart and

arteries; and that this continues till the spasm is relaxed or

overcome.' _Cullen's Works_, vol. i. p. 494.

[843] 'Such, however, is, at the same time, the nature of the animal

economy, that this debility proves an indirect stimulus to the

sanguiferous system; whence, by the intervention of the cold stage

and spasm connected with it, the action of the heart and larger

arteries is increased, and continues so till it has had the effect

of restoring the energy of the brain, of extending this energy to

the extreme vessels, of restoring, therefore, their action, and

thereby especially overcoming the spasm affecting them; upon the

removing of which, the excretion of sweat, and other marks of the

relaxation of excretories, take place.' _Practice of Physic_, in

_Cullen's Works_, vol. i. pp. 501, 502. See also p. 636, § cciii.

Or, as he elsewhere expresses himself (vol. i. p. 561): 'With

regard to the event of fevers, this is the fundamental principle:

_in fevers, nature cures the disease_; that is, certain motions

tending to death continue the disease, but, in consequence of the

laws of the animal economy, other motions are excited by these

which have a tendency to remove it.'

[844] 'If we may trust to our conclusions with respect to the proximate

cause, it follows, most naturally, from the view there given, that

the continued fever is always owing to an excess of spasm, or to

an excess of debility: as the one or other of these prevails, it

will give one or other of the two forms, either the Synocha or

inflammatory fever, or the Typhus or nervous fever.' _Cullen's

Works_, vol. i. p. 518.

A similar process of thought gave birth to his _Nosology_, or general

classification of diseases, which some have regarded as the most valuable

part of his labours;[845] though, for reasons already mentioned, we

must, I think, reject all such attempts as premature, and as likely to

work more harm than good, unless they are simply used as a contrivance to

aid the memory. At all events, the _Nosology_ of Cullen, though it

exhibits clear traces of his powerful and organizing mind, is fast

falling into disrepute, and we may be sure, that, for a long time yet, a

similar fate will await its successors. Our pathological knowledge is

still too young for so great an enterprise.[846] We have every reason to

expect, that, with the aid of chemistry, and of the microscope, it will

continue to grow more rapidly than it has hitherto done. Without

venturing to predict the rate of its increase, we may form some idea of

it, by considering what has been effected with resources very inferior to

those we now possess. In a work of great authority, published in the year

1848, it is stated, that since the appearance of Cullen's _Nosology_, our

mere enumeration of diseases has almost doubled, while our knowledge of

the facts relating to disease has more than doubled.[847]

[845] 'Cullen's most esteemed work is his _Nosology_.' _Hamilton's

History of Medicine_, London, 1831, vol. ii. p. 279. 'His

_Nosology_ will probably survive all his other works; it is

indisputably the best system which has yet appeared.' _Lives of

British Physicians_, London, 1830, p. 213. 'Celle de Cullen, qui

parut en 1772, et qui constitue un véritable progrès.' _Renouard_,

_Histoire de la Médecine_, Paris, 1846, vol. ii. p. 231. See also

_Hooper's Medical Dictionary_, edited by Dr. Grant, London, 1848,

p. 937. But, in the most celebrated medical works which have

appeared in England during the last twelve or fifteen years, I

doubt if there is any instance of the adoption of Cullen's

nosological arrangement. Abroad, and particularly in Italy, it is

more valued.

[846] 'I had rather not be cramped and hampered by attempting what abler

heads than mine have failed to achieve, and what, in truth, I

believe, in the present state of our science, to be impossible, a

complete methodical system of nosology.' _Watson's Principles and

Practice of Physic_, London, 1857, vol. i. p. 9. This is the

wisdom of a powerful understanding.

[847] 'Now, when the diseases of Cullen's nosology have been almost

doubled, and the facts relating to them have been more than

doubled.' _Williams' Principles of Medicine_, London, 1848,

p. 522.

I have now only one more name to add to this splendid catalogue of the

great Scotchmen of the eighteenth century.[848] But it is the name of a

man, who, for comprehensive and original genius, comes immediately after

Adam Smith, and must be placed far above any other philosopher whom

Scotland has produced. I mean, of course, John Hunter, whose only fault

was, an occasional obscurity, not merely of language, but also of

thought. In this respect, and, perhaps, in this alone, Adam Smith had the

advantage; for his mind was so flexible, and moved so freely, that even

the vastest designs were unable to oppress it. With Hunter, on the

contrary, it sometimes seemed as if the understanding was troubled by the

grandeur of his own conceptions, and doubted what path it ought to take.

He hesitated; the utterance of his intellect was indistinct.[849] Still,

his powers were so extraordinary, that, among the great masters of

organic science, he belongs, I apprehend, to the same rank as Aristotle,

Harvey, and Bichat, and is somewhat superior either to Haller or Cuvier.

As to this classification, men will differ, according to their different

ideas of the nature of science, and, above all, according to the extent

to which they appreciate the importance of philosophic method. It is from

this latter point of view that I have, at present, to consider the

character of John Hunter; and, in tracing the movements of his most

remarkable mind, we shall find, that, in it, deduction and induction were

more intimately united than in any other Scotch intellect, either of the

seventeenth or eighteenth century. The causes of this unusual

combination, I will now endeavour to ascertain. When they are understood,

they will not only explain many peculiarities in his works, but will

afford materials for speculation, to those who love to examine the

development of ideas, and who are able to discern the way in which

different schemes of national thought have given different shapes to

national character, and have thereby modified the whole course of human

affairs, to an extent of which the ordinary compilers of history have not

the slightest suspicion.

[848] I had intended giving some account of the once celebrated

Brunonian system, which was founded by Dr. John Brown, who was

first the pupil of Cullen, and afterwards his rival. But a careful

perusal of his works has convinced me that the real basis of his

doctrine, or the point from which he started, was not pathology,

but therapeutics. His hasty division of all diseases into sthenic

and asthenic, has no claim to be deemed a scientific

generalization, but was a mere artificial arrangement, resulting

from a desire to substitute a stimulating treatment in the place

of the old lowering one. He, no doubt, went to the opposite

extreme; but that being a purely practical subject, this

Introduction has no concern with it. For the same reason, I omit

all mention of Currie, who, though an eminent therapeutician, was

a commonplace pathologist. That so poor and thinly-peopled a

country as Scotland, should, in so short a period, have produced

so many remarkable men, is extremely curious.

[849] Mr. Ottley (_Life of Hunter_, p. 186) says, 'In his writings we

occasionally find an obscurity in the expression of his thoughts,

a want of logical accuracy in his reasonings, and an incorrectness

in his language, resulting from a deficient education.' But, a

deficient education will never make a man obscure. Neither will a

good education make him lucid. The only cause of clearness of

expression is clearness of thought; and clearness of thought is a

natural gift, which the most finished and systematic culture can

but slightly improve. Uneducated men, without a thousandth part of

John Hunter's intellect, are often clear enough. On the other

hand, it as frequently happens that men, who have received an

excellent education, cannot speak or write ten consecutive

sentences which do not contain some troublesome ambiguity. In

Hunter's works such ambiguities are abundant; and this is probably

one of the reasons why no one has yet given a connected view of

his philosophy. On his obscurity, compare _Cooper's Life of Sir

Astley Cooper_, London, 1843, vol. i. pp. 151, 152; _Paget's

Lectures on Surgical Pathology_, London, 1853, vol. i. p. 419; and

the remarks of his enemy, Foot, in _Foot's Life of Hunter_,

London, 1794, p. 59.

Hunter remained in Scotland till the age of twenty, when he settled in

London; and, though he was abroad for about three years, he abandoned his

own country, and became, socially and intellectually, a native of

England.[850] Hence, the early associations of his mind were formed in

the midst of a deductive nation; the later associations, in the midst of

an inductive one. For twenty years he lived among a people, who are,

perhaps, the acutest reasoners in Europe, if you concede to them the

principles from which they reason; but who, on the other hand, owing to

their proneness to this method, are so greedy after general principles,

that they will accept them on almost any evidence, and are, therefore, at

once very credulous and very logical. In that school, and surrounded by

those habits, the intellect of John Hunter was nurtured during the most

impressible period of his life. Then the scene suddenly shifted. Coming

to England, he passed forty years in the heart of the most empirical

nation in Europe; a nation utterly abhorring all general principles,

priding itself on its common sense, boasting, and with good reason too,

of its practical sagacity, proclaiming aloud the superiority of facts

over ideas, and despising every theory, unless some direct and immediate

benefit could be expected to accrue from it. The young and ardent

Scotchman found himself transplanted into a country totally different

from that which he had just quitted; and such a difference could not fail

to influence his mind. He saw, on every side, marks of prosperity, and of

long and uninterrupted success, not only in practical, but also in

speculative, life; and he was told that these things were effected by a

system which made facts the first consideration. He was ambitious of

fame, but he perceived that the road to fame was not the same in England

as in Scotland. In Scotland, a great logician would be deemed a great

man; in England, little account would be made of the beauty of his logic,

unless he was careful that the premisses from which he argued, were

trustworthy, and verified by experience. A new machine, a new experiment,

the discovery of a salt, or of a bone, would, in England, receive a wider

homage, than the most profound speculation from which no obvious results

were apprehended. That this way of contemplating affairs has produced

great good, is certain. But it is also certain, that it is a one-sided

way, and satisfies only part of the human mind. Many of the noblest

intellects crave for something which it cannot supply. In England,

however, during the greater part of the eighteenth century, it was even

more supreme than it is now, and was, indeed, so universal, that, from

the year 1727 until nearly the close of the century, our country did not

possess, in any branch of science, a speculator who had sufficient force

to raise himself above those narrow views which were then deemed the

perfection of wisdom.[851] Much was added to our knowledge, but its

distant boundaries were not enlarged. Though there was an increase of

curious and valuable details, and though several of the small and

proximate laws of nature were generalized, it must be admitted, that

those lofty generalizations, which we owe to the seventeenth century,

remained stationary, and that no attempt was made to push beyond them.

When John Hunter arrived in London, in 1748, Newton had been dead more

than twenty years, and the English people, absorbed in practical

pursuits, and now beginning, for the first time, to enter into political

life, had become more averse than ever to inquiries which aimed at truth

without regard to utility, and had accustomed themselves to value science

chiefly for the sake of the direct and tangible benefit which they might

hope to derive from it.

[850] He was born in 1728, and came to London in 1748. _Adams' Life of

John Hunter_, 2nd edit. London, 1818, pp. 20, 203. According to

Adams (pp. 30-35), he was abroad as surgeon in the English army

from 1761 to 1763; though, in _Foot's Life of Hunter_, London,

1794, p. 78, he is said to have returned to England in 1762. Mr.

Ottley says that he returned in 1763. _Ottley's Life of Hunter_,

p. 22, in vol. i. of _Hunter's Works_, edited by Palmer, London,

1835.

[851] See _Buckle's History of Civilization_, vol. ii. pp. 374, 375.

That Hunter must have been influenced by these circumstances, will be

obvious to whoever considers how impossible it is for any single mind to

escape from the pressure of contemporary opinion. But, inasmuch as all

his early associations had inclined him in another direction, we perceive

that, during his long residence in England, he was acted on by two

conflicting forces. The country of his birth made him deductive; the

country of his adoption made him inductive. As a Scotchman, he preferred

reasoning from general principles to particular facts; as an inhabitant

of England, he became inured to the opposite plan of reasoning from

particular facts to general principles. In every country, men naturally

give the first place to what is most valued. The English respect facts

more than principles, and therefore begin with the facts. The Scotch

consider principles as most important, and therefore begin with the

principles. And, I make no doubt that one of the reasons why Hunter, in

investigating a subject, is often obscure, is that, on such occasions,

his mind was divided between these two hostile methods, and that, leaning

sometimes to one and sometimes to the other, he was unable to determine

which he should choose. The conflict darkened his understanding. Adam

Smith, on the other hand, in common with all the great Scotchmen who

remained in Scotland, was remarkably clear. He, like Hume, Black, and

Cullen, never wavered in his method. These eminent men were not acted on

by English influence. Of all the most illustrious Scotchmen of the

eighteenth century, Hunter alone underwent that influence, and he alone

displayed a certain hesitation and perplexity of thought, which seems

unnatural to so great a mind, and which, as it appears to me, is best

explained by the peculiar circumstances in which he was placed.

One of the ablest of his commentators has justly observed, that his

natural inclination was, to conjecture what the laws of nature were, and

then reason from them, instead of reasoning to them by slow and gradual

induction.[852] This process of deduction was, as I have shown, the

favourite method of all Scotchmen, and, therefore, was precisely the

course which we should have expected him to adopt. But, inasmuch as he

was surrounded by the followers of Bacon,[853] this natural bias was

warped, and a large part of his marvellous activity was employed in

observations and experiments, such as no Scotch thinker, living in

Scotland, would ever have engaged in. He himself declared, that thinking

was his delight;[854] and there can be no doubt that, had he been

differently situated, thinking would have been his principal pursuit. As

it was, the industry with which he collected facts, is one of the most

conspicuous features in his career. His researches covered the whole

range of the animal kingdom, and were conducted with such untiring zeal,

that he dissected upwards of five hundred different species, exclusive of

dissections of different individuals, and exclusive, too, of dissections

of a large number of plants.[855] The results were carefully arranged and

stored up in that noble collection which he formed, and of the magnitude

of which we may gain some idea from the statement, that, at his death, it

contained upwards of ten thousand preparations illustrative of the

phenomena of nature.[856] By this means, he became so intimately

acquainted with the animal kingdom, that he made a vast number of

discoveries, which, considered singly, are curious, but which, when put

together, constitute an invaluable body of new truths. Of these, the most

important are, the true nature of the circulation in crustacea and

insects;[857] the organ of hearing in cephalopods;[858] the power

possessed by mollusks of absorbing their shells;[859] the fact that bees

do not collect wax, but secrete it;[860] the semicircular canals of the

cetacea;[861] the lymphatics of birds;[862] and the air-cells in the

bones of birds.[863] We are also assured, that he anticipated the recent

discoveries respecting the embryo of the kangaroo;[864] and his published

works prove, that, in the human subject, he discovered the muscularity of

the arteries,[865] the muscularity of the iris,[866] and the digestion

of the stomach after death by its own juice.[867] Although, in his time,

animal chemistry was not yet raised to a system, and was consequently

little heeded by physiologists, Hunter endeavoured, by its aid, to search

out the qualities of the blood, so as to ascertain the properties of its

constituents.[868] He also examined it in different stages of embryonic

life, and by minutely tracking it through its periods of development, he

made the capital discovery, that the red globules of the blood are formed

later than its other components. His contemporaries, however, were so

little alive to the importance of this great physiological truth, that it

fell dead upon them, and, being forgotten, it was, about fifty years

afterwards, rediscovered, and was announced, in 1832, as a law of nature

which had just been brought to light.[869] This is one of many instances

in the history of our knowledge, which proves how useless it is for a man

to advance too far beyond the age in which he lives.[870] But Hunter,

besides making the discovery, also saw its meaning. From it, he inferred

that the function of the red globules is to minister to the strength of

the system, rather than to its repair.[871] This is now universally

admitted; but it was not admitted till long after his death. Its

recognition is chiefly owing to the rapid advance of animal chemistry,

and to improvements in the microscope. For, by the employment of these

resources, it has become manifest, that the red globules, the respiratory

process, the production of animal heat, and the energy of the locomotive

organs, are but different parts of a single scheme.[872] Their connexion

with each other is established, not only by a comparison of different

species, but also by a comparison of different members of the same

species. In human beings, for example, the locomotive and other animal

functions are more active in persons of a sanguine temperament than in

those of a lymphatic temperament; while, in sanguine temperaments, the

globules are more numerous than in lymphatic ones. The knowledge of this

fact we owe to Lecanu;[873] and to him we are also indebted for an

analogous fact, corroborating the same view. He has shown, that the blood

of women contains more water and fewer red globules than the blood of

men;[874] so that here again we discern the relation between these

globules and the energy of animal life. Inasmuch, however, as these

researches were not made until many years after the death of Hunter, the

coincidence between them and his speculative conclusions is a striking

instance of his power of generalization, and of that unrivalled knowledge

of comparative anatomy, which supplied him with materials from which, in

spite of the backwardness of animal chemistry, he was able to draw an

inference, which later and minuter researches have decisively

verified.[875]

[852] 'He followed his natural inclination. He preferred the more

delusive, apparently the more direct, road, which has seduced so

many philosophers. He sought to arrive at the general laws of

nature at once by conjecture: rather than, by a close and detailed

study of her inferior operations, to ascend, step by step, through

a slow and gradual induction to those laws which govern her

general procedure.' Babington's Preface to Hunter's _Treatise on

the Venereal Disease_, in _Hunter's Works_, vol. ii. p. 129.

Compare the narrow and carping criticism in _Foot's Life of

Hunter_, p. 163.

[853] That I may not be suspected of exaggeration, I will quote what by

far the greatest of all the historians of medicine has said upon

this subject. 'La majorité des médecins qui prétendaient s'être

formés d'après Bâcon, n'avaient hérité de lui qu'une répugnance

invincible pour les hypothèses et les systèmes, une grande

vénération pour l'expérience, et un désir extrême de multiplier le

nombre des observations. Ce fut chez les Anglais que la méthode

empirique en médecine trouva le plus de partisans, et c'est

principalement aussi chez eux qu'elle s'est répandue jusqu'aux

temps les plus rapprochés de nous. Sa propagation y fut favorisée,

non-seulement par le profond respect que les Anglais continuent

toujours de porter à l'immortel chancelier, mais encore par la

haute importance que la nation entière attache au sens commun,

_common sense_, et elle y demeura l'ennemie irréconciliable de

tous les systèmes que ne reposent pas sur l'observation.'

_Sprengel, Histoire de la Médecine_, vol. v. p. 411, Paris, 1815.

[854] Clive says, 'Much as Mr. Hunter did, he thought still more. He has

often told me, his delight was, to think.' _Abernethy's Hunterian

Oration_, London, 1819, p. 26.

[855] Mr. Owen, in his interesting Preface to the fourth volume of

_Hunter's Works_, says (p. vii.), 'There is proof that Hunter

anatomized at least five hundred different species of animals,

exclusive of repeated dissections of different individuals of the

same species, besides the dissections of plants to a considerable

amount.'

[856] 'Some idea may be formed of Hunter's extraordinary diligence, by

the fact, that his museum contained, at the time of his death,

upwards of 10,000 preparations, illustrative of human and

comparative anatomy, physiology, and pathology, and natural

history.' _Weld's History of the Royal Society_, London, 1848,

vol. ii. p. 92.

[857] 'I have tested the conflicting evidence of these observers by

dissection of the heart in the lobster; and you will perceive by

this preparation that it is more complicated than even the Danish

naturalist supposed, and fully bears out the opinion of Hunter in

regard to the mixed nature of the circulation in the crustacea.'

_Owen's Lectures on the Comparative Anatomy and Physiology of the

Invertebrate Animals_, 2nd edit. London, 1855, p. 318. 'Cuvier,

misled by the anomalous diffused condition of the venous system,

supposed that there was no circulation of the blood in insects;

yet the dorsal vessel was too conspicuous a structure to be

overlooked. Such, however, was the authority of the great

anatomist, that the nature of the heart began to be doubted, and

the strangest functions to be attributed to it. Hunter, however,

who was prepared to appreciate the true state of the circulating

system in insects, by his discovery of the approximately diffused

and irregular structure of the veins in the crustacea, has

described, in his work on the blood, all the leading characters of

the circulation in insects as it is recognized by comparative

physiologists of the present day.' _Ibid._ p. 383. Compare

_Hunter's Essays and Observations on Natural History_, London,

1861, vol. i. p. 108.

[858] 'The class called Sepia has the organ of hearing, though somewhat

differently constructed from what it is in fishes.' _An Account of

the Organ of Hearing in Fishes_, in _Hunter's Works_, vol. iv. p.

294. At the bottom of the page Mr. Owen observes, in a note, 'This

is the first announcement of the existence of an organ of hearing

in the Cephalopoda.'

[859] 'Hunter discovered that the molluscous inhabitant of a shell had

the power of absorbing part of its dwelling.' _Owen's Lectures on

the Comparative Anatomy and Physiology of the Invertebrate

Animals_, London, 1855, p. 544. 'Every shell-fish has the power of

removing a part of its shell, so as to adapt the new and the old

together, which is not done by any mechanical power, but by

absorption.' _Anatomical Remarks on a New Marine Animal_, in

_Hunter's Works_, vol. iv. p. 469, edit. Palmer. In a note to this

passage, it is said, that 'the doctrine of the absorption of shell

has been lately' (_i.e._ in 1833) 'adduced as a new discovery.'

[860] 'His keen observation did not fail to detect several errors which

preceding naturalists had fallen into, especially with regard to

the formation of the wax, which he proved to be secreted, not

collected, by the animal.' _Ottley's Life of Hunter_, p. 122. 'The

wax is formed by the bees themselves; it may be called an external

secretion of oil, and I have found that it is formed between each

scale of the under side of the belly.' _Observations on Bees_, in

_Hunter's Works_, vol. iv. p. 433.

[861] 'In the terminating part there are a number of perforations into

the cochlea, and one into the semicircular canals, which afford a

passage to the different divisions of the auditory nerve.'

_Observations on the Structure and [OE]conomy of Whales_, in

_Hunter's Works_, vol. iv. pp. 383, 384. 'The semicircular canals

of the cetacea, described by Hunter in the paper on Whales, a

structure which Cuvier rightly states that Camper overlooked, but

incorrectly claims the discovery as his own.' Preface to vol. iv.

of _Hunter's Works_, p. xxi.

[862] Dr. Adams, in his somewhat hasty _Life of Hunter_, says (pp. 27,

28), 'Mr. Hewson always claimed the discovery of lymphatics in

birds.' But the truth is, that Hewson never claimed it. He says,

'It may be necessary to mention here, that the dispute between Dr.

Monro and me is, who first discovered the lacteals of birds? for

as to the lymphatics in their necks (mentioned in this gentleman's

note), these we both allow were discovered by Mr. John Hunter,

about ten years ago.' And, again, 'These lymphatics in the necks

of fowls were first discovered by Mr. John Hunter.' _Hewson's

Works_, edit. Gulliver (Sydenham Soc.), pp. 102, 145.

[863] _Hunter's Works_, vol. iv. pp. xxi. 176.

[864] 'See Nos. 3731, 3734, 3735, in the Physiological series of the

Hunterian Museum, in which there are evidences that Mr. Hunter had

anticipated most of the anatomical discoveries which have

subsequently been made upon the embryo of the Kangaroo.' _Rymer

Jones' Organization of the Animal Kingdom_, London, 1855, pp. 829,

830.

[865] 'The muscularity of arteries, of which John Hunter made

physiological proof, is now a matter of eyesight.' _Simon's

Pathology_, London, 1850, p. 69. 'To prove the muscularity of an

artery, it is only necessary to compare its action with that of

elastic substances.' ... 'When the various uses of arteries are

considered, such as their forming different parts of the body out

of the blood, their performing the different secretions, their

allowing at one time the blood to pass readily into the smaller

branches, as in blushing, and at another, preventing it

altogether, as in paleness from fear: and if to these we add the

power of producing a diseased increase of any or every part of the

body, we cannot but conclude that they are possessed of muscular

powers.' _Hunter's Works_, vol. iii. p. 157. See also vol. iv.

p. 254. Mr. Gulliver, in his edition of _Hewson's Works_, London,

1846, says (p. 125), that Hunter's 'experiments on the functions

of the arteries are supported by the latest and best observations

on their structure.'

[866] 'The fact of the muscularity of the iris, which is here presumed

from analogy by Mr. Hunter, has been since directly proved by the

observations of Bauer and Jacob (_Phil. Trans._ 1822), and

indirectly by Berzelius, who found that the iris possesses all the

chemical properties of muscle.' Palmer's note in _Hunter's Works_,

vol. iii. p. 146, London, 1837.

[867] _Adams' Life of Hunter_, pp. 59, 60, 245. _Hunter's Works_, vol. i.

p. 43, vol. iv. pp. 116-121. _Watson's Principles of Physic_,

vol. ii. p. 440.

[868] 'Hunter subjects the blood to both mechanical and chemical

analysis, and endeavours to determine the characteristic

properties of its different constituents.' Owen's Preface to vol.

iv. of _Hunter's Works_, p. xii. But this gives, perhaps, rather

too high an idea of his animal chemistry; for such was then the

miserable state of this extremely important branch of knowledge,

that he arrived at the conclusion that 'blood gives no analysis

excepting that of common animal matter.' _Principles of Surgery_,

chap. iii. in _Hunter's Works_, vol. i. p. 229.

[869] 'In seeking to determine the respective importance of the different

constituents of the blood, by the philosophical and most difficult

inquiry into their respective periods of formation in the

development of the embryo, Hunter made the interesting discovery

that the vessels of the embryo of a red-blooded animal circulated

in the first instance colourless blood, as in the invertebrate

animals. 'The red globules,' he observes, 'seemed to be formed

later in life than the other two constituents, for we see while

the chick is in the egg the heart beating, and it then contains a

transparent fluid before any red globules are formed, which fluid

we may suppose to be the serum and the lymph.' I well remember the

feelings of surprise with which I listened, while at Paris in

1832, to a memoir read before the Academy of Science, by MM.

Delpech and Coste, the object of which was the announcement of the

same fact as a novel and important discovery. The statement of the

French observers was received with all the consideration which its

importance justly merited, without its being suspected that our

great physiologist had, half a century before, embraced it, with

all its legitimate deductions, in the extended circle of his

investigations.' Owen's Preface to vol. iv. of _Hunter's Works_,

p. xiii.

[870] Indeed, if we may rely on the references recently given by Mr.

Gulliver, which, from his great general accuracy, there seems no

reason to question, the fact that the pale blood precedes the red,

was known even in the time of Glisson. See Gulliver's learned

edition of _Hewson's Works_, London, 1846, p. 222. But, to the

contemporaries of Glisson, such a fact was isolated, and

consequently useless. Nothing is valuable while it appears to

stand alone.

[871] 'From the above account, it appears that whatever may be their

utility in the machine, the red globules certainly are not of such

universal use as the coagulating lymph, since they are not to be

found in all animals, _nor so early in those that have them_; nor

are they pushed into the extreme arteries, where we must suppose

the coagulating lymph reaches; neither do they appear to be so

readily formed. This being the case, _we must conclude them not to

be the important part of the blood in contributing to growth,

repair, &c. Their use would seem to be connected with strength._'

_A Treatise on the Blood, Inflammation, and Gunshot Wounds_, in

_Hunter's Works_, vol. iii. p. 68. In another remarkable passage,

he touches on the possibility of an increase in the amount of red

globules being connected with an increase in the amount of heat.

'I will not pretend to determine how far this may assist in

keeping up the animal heat.' _Observations on the Structure and

[OE]conomy of Whales_, in _Hunter's Works_, vol. iv. p. 364.

[872] The evidence of this is collected in the notes to _Buckle's

History of Civilization_, vol. i. pp. 58-61.

[873] 'According to Lecanu, temperament has an influence upon the

composition of the blood. He infers from his analyses that the

blood of lymphatic persons is poorer in solid constituents, and

especially in blood corpuscules, than that of persons of

sanguineous temperament, while the quantity of albumen is much the

same in both.' _Simon's Animal Chemistry with reference to the

Physiology and Pathology of Man_, London, 1845, vol. i. p. 236.

Compare _Thomson's Chemistry of Animal Bodies_, Edinburgh, 1843,

p. 370.

[874] _Simon's Animal Chemistry_, vol. i. pp. 234, 235. Subsequent

experiments have confirmed this. 'The proportion of red globules

_dried_ to 1000 parts of blood, is in healthy males estimated at

127 parts by Andral and Gavarret; lower and higher figures have

been given by other analysts, but this probably is the result of

somewhat different modes of proceeding. _In females the proportion

of globules is lower._ Becquerel and Rodier make the difference to

be about 15 parts per 1000.' _Jones and Sieveking's Pathological

Anatomy_, London, 1854, p. 23. Hence, the greater specific gravity

of male blood. See the interesting results of Dr. Davy's

experiments in _Davy's Physiological and Anatomical Researches_,

London, 1839, vol. ii. p. 32.

[875] Hunter died in 1793. The researches of Lecanu were published in

1831.

Another, and still more remarkable proof of the extent to which

Hunter outstripped his own age, appears in the following passage,

which has just been published in his posthumous works, and in

which he anticipates the grandest and most suggestive of all the

ideas belonging to the physiology of the nineteenth century. 'If

we were capable of following the progress of increase of the

number of the parts of the most perfect animal, as they first

formed in succession, from the very first to its state of full

perfection, we should probably be able to compare it with some one

of the incomplete animals themselves, of every order of animals in

the Creation, being at no stage different from some of the

inferior orders. Or, in other words, if we were to take a series

of animals, from the more imperfect to the perfect, we should

probably find an imperfect animal, corresponding with some stage

of the most perfect.' _Essays and Observations by John Hunter,

being his Posthumous Papers_, London, 1861, vol. i. p. 203.