Necker's wish to have individuals marked by external form.
If, instead of this, we are contented to take for an
individual that portion of a mass, of whatever form, which
is connected by the continuous influence of the same
crystalline forces, by whatever incidents these forces may
be manifested, (as cleavage, {158} physical and optical
properties, and the like,) our mode of proceeding avoids all
the above inconveniences, applies alike to the most perfect
and most imperfect specimens, and gives a result agreeable
to the general analogy of natural history, and the rules of
its methods[78\8].
[Note 78\8: I will not again enter into the subject of
Nomenclature; but I may remark that M. Necker has adopted
(i. 415) the Nomenclature of Beudant, latinizing the names,
and thus converting each into a single word. He has also
introduced, besides the names of Genera, names of Families
taken from the _typical_ Genus. Thus the Family of
_Carbonidiens_ contains the following genera:
_Calcispathum_, _Magnesispathum_, _Dolomispathum_,
_Ferrispathum_, _&c._, _Malachita_, _Azuria_, _Gaylusacia_.]
I now quit the subject of mere Resemblance, and proceed to
treat of that natural affinity which Natural Systems of
Classification for organic bodies must involve.
{{159}}
CHAPTER IV.
OF THE IDEA OF NATURAL AFFINITY.
1. IN the Second Chapter of this Book it was shown that
although the Classificatory Sciences proceed ostensibly upon
the Idea of Resemblance as their main foundation, they
necessarily take for granted in the course of their progress
a further Idea of Natural Affinity. This appeared[79\8] by a
general consideration of the nature of Science, by the
recognition of natural species and genera, even in
Artificial Systems of Classification[80\8], and by the
**attempts of botanists to form a Natural System. It further
appeared that among the processes by which endeavours have
been made to frame a Natural System, some, as the method of
_Blind Trial_ and the method of _General Comparison_, have
been altogether unsuccessful, being founded only upon a
collection of resemblances, casual in the one case and
arbitrary in the other. In neither of these processes is
there employed any general principle by which we may be
definitely directed as to what resemblances we should
employ, or by which the result at which we arrive may be
verified and confirmed. Our object in the present chapter is
to show that the Idea of Natural Affinity supplies us with a
principle which may answer such purposes.
[Note 79\8: Art. 5.]
[Note 80\8: Art. 7.]
I shall first consider the Idea of Affinity as exemplified
in organized beings. In doing this, we may appear to take
for granted Ideas which have not yet come under our
discussion, as the Ideas of Organization, and Vital
Function; but it will be found that the principle to which
we are led is independent of these additional Ideas. {160}
2. We have already seen that the attempts to discover the
divisions which result from this Natural Affinity have led
to the consideration of the _Subordination of Characters_.
It is easy to see that some organs are more essential than
others to the existence of an organized being; the organs of
nutrition, for example, more essential than those of
locomotion. But at the same time it is clear that any
_arbitrary_ assumption of a certain scale of relative values
of different kinds of characters will lead only to an
Artificial System. This will happen, if, for example, we
begin by declaring the nutritive to be superior in
importance to the reproductive functions. It is clear that
this relation of importance of organs and functions must be
collected by the study of the organized beings; and cannot
be determined _à priori_, without depriving us of all right
to expect a general accordance between our system and the
arrangement of nature. We see, therefore, that our notion of
Natural Affinity involves in it this consequence;--that it
is not to be made out by an arbitrary subordination of characters.
3. The functions and actions of living things which we
separate from each other in our consideration, cannot be
severed in nature. Each function is essential; Life implies
a collection of movements, and ceases when any of these
movements is stopped. A change in the organization
subservient to one set of functions may lead necessarily to
a change in the organization belonging to others. We can
often see this necessary connexion; and from a comparison of
the forms of organized beings,--from the way in which their
structure changes in passing from one class to another, we
are led to the conviction that there is some general
principle which connects and graduates all such changes.
When the circulatory system changes, the nervous system
changes also: when the mode of locomotion changes, the
respiration is also modified.
4. These corresponding changes may be considered as ways in
which the living thing is fitted to its mode of life; as
marks of _adaptation to a purpose_; or, as it has been
otherwise expressed, as results of the {161} _conditions of
existence_. But at the present moment, we put forward these
correspondencies in a different light. We adduce them as
illustrations of what we mean by Affinity, and what we
consider as the tendency of a Natural Classification. It has
sometimes been asserted that if we were to classify any of
the departments of organized nature by means of one
function, and then by means of another, the two
classifications, if each strictly consistent with itself,
would be consistent with each other. Such an assertion is
perhaps more than we are entitled to make with confidence;
but it shows very well what is meant by Affinity. The
disposition to believe such a general identity of all
partial natural classifications, shows how readily we fix
upon the notion of Affinity, as a general result of the
causes which determine the forms of living things. When
these causes or principles, of whatever nature they are
conceived to be, vary so as to modify one part of the
organization of the being, they also modify another: and
thus the groups which exhibit this variation of the
fundamental principles of form, are the same, whether the
manifestation of the change be sought in one part or in
another of the organized structure. The groups thus formed
are related by Affinity; and in proportion as we find the
evidence of more functions and more organs to the propriety
of our groups, we are more and more satisfied that they are
Natural Classes. It appears, then, that our Idea of Affinity
involves the conviction of the _Coincidence of natural
arrangements formed on different functions_; and this,
rather than the principle of the Subordination of some
characters to others, is the true ground of the natural
method of Classification.
5. For example, Cuvier, after speaking of the Subordination
of Characters as the guide which he intends to follow in his
arrangement of animals, interprets this principle in such a
manner[81\8] as to make it agree nearly with the one just
stated: 'In pursuance of what has been said on methods in
general, we now require to {162} know what characters in
animals are the most influential, and therefore those which
must be made the grounds of the primary divisions.' 'These,'
he says, 'it is clear must be those which are taken from the
animal functions;--sensation and motion:'--But how does he
confirm this? Not by showing that the animal functions are
independent of, or predominant over, the vegetative, but by
observing that they follow the same gradations.
'Observation,' he continues, 'confirms this view, by showing
that the degrees of development and complication of the
animal functions agree with those of the vegetative. The
heart and the organs of the circulation are a sort of center
for the vegetative functions, as the brain and the trunk of
the nervous system are for the animal functions. Now we see
these two systems descend in the scale, and disappear the
one with the other. In the lowest animals, when there are no
longer any distinct nerves, there are also no longer
distinct fibres, and the organs of digestion are simply
hollowed out in the homogeneous mass of the body. The
muscular system disappears even before the nervous, in
insects; but in general the distribution of the medullary
masses corresponds to that of the muscular instruments; a
spinal cord, on which knots or ganglions represent so many
brains, corresponds to a body divided into numerous rings
and supported on pairs of members placed at different points
of the length, and so on.
[Note 81\8: _Règne Animal_, p. 55.]
'This _correspondence_ of the general forms which result
from the arrangement of the motive organs, from the
distribution of the nervous masses, and from the energy of
the circulatory system, must therefore form the ground of
the first great sections by which we divide the animal kingdom.'
6. Decandolle takes the same view. There must be, he says,
_an equilibrium_ of the different functions[82\8]. And he
exemplifies this by the case of the distinction of
monocotyledonous and dicotyledonous plants, which being at
first established by means of the organs of {163}
reproduction, was afterwards found to coincide with the
distinction of endogenous and exogenous, which depends on
the process of nutrition. 'Thus,' he adds, '_the natural
classes founded on one of the great functions of the
vegetable are necessarily the same as those which are
founded upon the other function_; and I find here a very
useful criterion to ascertain whether a class is natural:
namely, in order to announce that it is so, it must be
arrived at by the two roads which vegetable organization
presents. Thus I affirm,' he says, 'that the division of
monocotyledons from dicotyledons, and the distinction of
Gramineæ from Cyperaceæ, are real, because in these cases, I
arrive at the same result by the reproductive and the
nutritive organs; while the distinction of monopetalous and
polypetalous, of Rhodoraceæ and Ericineæ, appears to me
artificial, because I can arrive at it only by the
reproductive organs.'
[Note 82\8: _Theor. Elem._ p. 79.]
Thus the Correspondence of the indications of different
functions is the criterion of Natural Classes; and this
correspondence may be considered as one of the best and most
characteristic marks of the fundamental Idea of Affinity.
And the Maxim by which all Systems professing to be natural
must be tested is this:--that the _arrangement obtained from
one set of characters coincides with the arrangement
obtained from another set_.
This Idea of Affinity, as a natural connexion among various
species, of which connexion all particular resemblances are
indications, has principally influenced the attempts at
classifying the animal kingdom. The reason why the
classification in this branch of Natural History has been
more easy and certain than that of the vegetable world is,
as Decandolle says[83\8], that besides the functions of
nutrition and reproduction, which animals have in common
with plants, they have also in addition the function of
sensation; and thus have a new means of verification and
concordance. But we may add, as a further reason, that the
functions of {164} animals are necessarily much more obvious
and intelligible to us than those of vegetables, from their
clear resemblance to the operations which take place in our
own bodies, to which our attention has necessarily been
strongly directed.
[Note 83\8: _Theor. Elem._ p. 80.]
7. The question here offers itself, whether this Idea of
Natural Affinity is applicable to inorganic as well as to
organic bodies;--whether there be Natural Affinities among
Minerals. And to this we are now enabled to reply by
considering whether or not the principle just stated is
applicable in such cases. And the conclusion to which our
principle leads us is,--that there are such Natural
Affinities among Minerals, since there are different sets of
characters which may be taken, (and have by different
writers been taken,) as the basis of classification. The
hardness, specific gravity, colour, lustre, crystallization,
and other _external_ characters, as they are termed, form
one body of properties according to which minerals may be
classified; as has in fact been done by Mohs, Breithaupt,
and others. The _chemical_ constitution of the substances,
on the other hand, may be made the principle of their
arrangement, as was done by Haüy, and more recently, and on
a different scheme, by Berzelius. Which of these is the true
and natural classification? To this we answer, that _each_
of these arrangements is true and natural, then, and then
only, when it coincides with the other. An arrangement by
external characters which gives us classes possessing a
common chemical character;--a chemical order which brings
together like and separates unlike minerals;--such
classifications have the evidence of truth in their
agreement with one another. Every classification of minerals
which does not aim at and tend to such a result, is so far
merely arbitrary; and cannot be subservient to the
expression of general chemical and mineralogical truths,
which is the proper purpose of such a classification.
8. In the History of Mineralogy I have related the advances
which have been made among mineralogists and chemists in
modern times towards a System {165} possessing this
character of truth. I have there described the mixed systems
of Werner and Haüy;--the attempt made by Mohs to form a pure
Natural History system;--the first and second attempt of
Berzelius to form a pure chemical system; and the failure of
both these attempts. But the distinct separation of the two
elements of which science requires the coincidence threw a
very useful light upon the subject; and the succeeding mixed
systems, such as that of Naumann, approached much nearer to
the true conditions of the problem than any of the preceding
ones had done. Thus, as I have stated, several of Naumann's
groups have both a common chemical character and great
external resemblances. Such are his _Anhydrous Unmetallic
Haloids_--his _Anhydrous Metallic Haloids_--_Hydrous
Metallic Haloids_--_Oxides_ of metals--_Pyrites_--_Glances_--
Blendes_. The existence of such groups shows that we may hope
ultimately to obtain a classification of minerals which shall
be both chemically significant, and agreeable to the methods
of Natural History: although when we consider how very imperfect
as yet our knowledge of the chemical composition of minerals is,
we can hardly flatter ourselves that we shall arrive at such a
result very soon.
We have thus seen that in Mineralogy, as well as in the
sciences which treat of organized bodies, we may apply the
Idea of Natural Affinity; of which the fundamental maxim is,
that _arrangements obtained from different sets of
characters must coincide_.
Since the notion of Affinity is thus applicable to inorganic
as well as to organic bodies, it is plain that it is not a
mere modification of the Idea of Organization or Function,
although it may in some of its aspects appear to approach
near to these other Ideas. But these Ideas, or others which
are the foundation of them, necessarily enter in a very
prominent and fundamental manner into all the other parts of
Natural History. To the consideration of these, therefore,
we shall now proceed.
{{167}}
BOOK IX.
THE
PHILOSOPHY
OF
BIOLOGY.
LA vie est donc un TOURBILLON plus ou moins rapide, plus ou
moins compliqué, dont la direction est constante, et qui
entraine toujours des molecules de mêmes sorts, mais où les
molecules individuelles entrent et d'où elles sortent
continuellement, de manière que la _Forme_ du corps vivant
lui est plus essentielle que sa _Matière_.
Tant que ce mouvement subsiste, le corps où il s'exerce est
_vivant_; _il vit_. Lorsque le mouvement s'arrête sans
retour, le corps _meurt_.
CUVIER, _Règne Animal_, s. 12.
I REMEMBER, upon asking our famous Harvey, what induced him
to think of a circulation of the blood, he said, that
observing the valves in the veins of many parts of the body,
so placed as to give a free passage to the blood towards the
heart, but to oppose the passage of the venal blood the
contrary way, he imagined that so provident a cause as
nature had not thus placed so many valves without design;
and as no design seemed more probable than that the blood
could not well, because of the interposing valves, be sent
by the veins to the limbs, it should be sent through the
arteries and return through the veins when valves did not
oppose its course that way.
BOYLE, _On the Final Causes of Natural Things_. On the
Proposition: _'Tis often allowable for a naturalist, from the
manifest and apposite uses of the parts of animal bodies, to
collect some of the particular ends for which the Creator
designed them: and in some cases we may, from the known
nature and structure of the parts, draw particular
conjectures about the particular offices of them._
{{169}}
BOOK IX.
THE PHILOSOPHY OF BIOLOGY.
CHAPTER I.
ANALOGY OF BIOLOGY WITH OTHER SCIENCES.
1. IN the History of the Sciences, after treating of the
Sciences of Classification, we proceeded to what are there
termed the Organical Sciences, including in this term
Physiology and Comparative Anatomy. A peculiar feature in
this group of sciences is that they involve the notion of
_living_ things. The notion of _Life_, however vague and
obscure it may be in men's minds, is apprehended as a
peculiar Idea, not resolvable into any other Ideas, such,
for instance, as Matter and Motion. The separation between
living creatures and inert matter, between organized and
unorganized beings, is conceived as a positive and
insurmountable barrier. The two classes of objects are
considered as of a distinct kind, produced and preserved by
different forces. Whether the Idea of Life is really thus
original and fundamental, and whether, if so, it be one Idea
only, or involve several, it must be the province of true
philosophy to determine. What we shall here offer may be
considered as an attempt to contribute something to the
determination of these questions; but we shall perhaps be
able to make it appear that science is at present only in
the course of its progress towards a complete solution of
such problems.
Since the main feature of those sciences of which we have
now to examine the philosophy is, that they {170} involve
the Idea of Life, it would be desirable to have them
designated by a name expressive of that circumstance. The
word _Physiology_, by which they have most commonly been
described, means _the Science of Nature_; and though it
would be easy to explain, by reference to history, the train
of thought by which the word was latterly restricted to
_Living Nature_, it is plain that the name is,
etymologically speaking, loose and improper. The term
_Biology_, which means exactly what we wish to express, _the
Science of Life_, has often been used, and has of late
become not uncommon among good winters. I shall therefore
venture to employ it, in most cases, rather than the word
_Physiology_.
2. As I have already intimated, one main inquiry belonging
to the Philosophy of Biology, is concerning the Fundamental
Idea or Ideas which the science involves. If we look back at
the course and the results of our disquisitions respecting
other sciences in this work, and assume, as we may
philosophically do, that there will be some general analogy
between those sciences and this, in their development and
progress, we shall be enabled to anticipate in some measure
the nature of the view which we shall now have to take. We
have seen that in other subjects the Fundamental Ideas on
which science depended, and the Conceptions derived from
these, were at first vague, obscure, and confused;--that by
gradual steps, by a constant union of thought and
observation, these conceptions become more and more clear,
more and more definite;--and that when they approached
complete distinctness and precision, there were made great
positive discoveries into which these conceptions entered;
and thus the new precision of thought was fixed and
perpetuated in some conspicuous and lasting truths. Thus we
have seen how the first confused mechanical conceptions
(Force, and the like,) were, from time to time, growing
clearer, down to the epoch of Newton;--how true conceptions
of Genera and of wider classes, gradually unfolded
themselves among the botanists of the sixteenth and
seventeenth centuries;--how the idea of Substance became
steady enough to govern the {171} theories of chemists only
at the epoch of Lavoisier;--how the Idea of Polarity,
although often used by physicists and chemists, is even now
somewhat vague and indistinct in the minds of the greater
part of speculators. In like manner we may expect to find
that the Idea of Life, if indeed _that_ be the governing
Idea of the Science which treats of Living Things, will be
found to have been gradually approaching towards a distinct
and definite form among the physiologists of all ages up to
the present day. And if this be the case, it may not be
considered superfluous, with reference to so interesting a
subject, if we employ some space in tracing historically the
steps of this progress;--the changes by which the originally
loose notion of Life, or of Vital Powers, became more nearly
an Idea suited to the purposes of science.
3. But we may safely carry this analogy between Biology and
other sciences somewhat further. We have seen, in other
sciences, that while men in their speculations were thus
tending towards a certain peculiar Idea, but before they as
yet saw clearly that it was peculiar and independent, they
naturally and inevitably clothed their speculations in
conceptions borrowed from some other extraneous idea. And
the unsatisfactoriness of all such attempts, and the
necessary consequence of this, a constant alteration and
succession of such inappropriate hypotheses, were
indications and aids of the progress which was going on
towards a more genuine form of the science. For instance, we
have seen that in chemistry, so long as men refused to
recognize a peculiar and distinct kind of power in the
_Affinity_ which binds together the elements of bodies, they
framed to themselves a series of hypotheses, each
constructed according to the prevalent ideas of the time, by
which they tried to represent the relation of the compound
to the ingredients:--first, supposing that the elements
bestowed upon the whole qualities _resembling_ their
own:--then giving up this supposition, and imagining that
the properties of the body depended upon the _shape_ of the
component particles;--then, as their view expanded, assuming
that it was {172} not the shape, but the mechanical _forces_
of the particles which gave the body its attributes;--and
finally acquiescing in, or rather reluctantly admitting, the
idea of _Affinity_, conceived as a peculiar power, different
not only from material contact, but from any mechanical or
dynamical attraction.
Now we cannot but think it very natural, if we find that the
history of Biology offers a series of occurrences of the
same nature. The notions of Life in general, or of any Vital
Functions or Vital Forces in particular, are obviously very
loose and vague as they exist in the minds of most men. The
discrepancies and controversies respecting the definitions
of all such terms, which are found in all works on
physiology, afford us abundant evidence that these notions
are not, at least not generally, apprehended with complete
clearness and steadiness. We shall therefore find approaches
and advances, intermediate steps, gradually leading up to
the greatest degree of distinctness which has yet been
attained. And in those stages of imperfect apprehension in
which the notions of Life and of Vital Powers are still too
loose and unformed to be applied independently, we may
expect to find them supported and embodied by means of
hypotheses borrowed from other subjects, and thus, made so
distinct and substantial as to supply at least a temporary
possibility of scientific reasoning upon the laws of life.
4. For example, if we suppose that men begin to speculate
upon the properties of living things, not acknowledging a
peculiar Vital Power, but making use successively of the
knowledge supplied by the study of other subjects, we may
easily imagine a series of hypotheses along which they would pass.
They would probably, first, in this as in other sciences,
have their thoughts occupied by vague and _mystical_ notions
in which material and spiritual agency, natural and
supernatural events, were mixed together without
discrimination, and without any clear notion at all. But as
they acquired a more genuine perception of the nature of
**knowledge, they would naturally try to explain vital
motions and processes by means of {173} such forces as they
had learnt the existence of from other sciences. They might
first have a _mechanical_ hypothesis, in which the
mechanical _Forces_ of the solids and fluids which compose
organized bodies should be referred to, as the most
important influences in the process of life. They might then
attend to the actions which the fluids exercise in virtue of
their _Affinity_, and might thus form a _chemical_ theory.
When they had proved the insufficience of these hypotheses,
borrowed from the powers which matter exhibits in other
cases, they might think themselves authorized to assume some
peculiar power or agency, still material, and thus they
would have the hypothesis of a _Vital Fluid_. And if they
were driven to reject this, they might think that there was
no resource but to assume an immaterial principle of life,
and thus they would arrive at the doctrine of an _Animal Soul_.
Now, through the cycle of hypotheses which we have thus
supposed, physiology has actually passed. The conclusions to
which the most philosophical minds have been led by a survey
of this progress is, that by the failure of all these
theories, men have exhausted this path of inquiry, and shown
that scientific truth is to be sought in some other manner.
But before I proceed further to illustrate this result, it
will be proper, as I have already stated, to exhibit
historically the various hypotheses which I have described.
In doing this I shall principally follow the _History of
Medicine_ of Sprengel. It is only by taking for my guide a
physiologist of acknowledged science and judgment, that I
can hope, on such a subject, to avoid errours of detail. I
proceed now to give in succession an account of the
Mystical, the Iatrochemical, the Iatromathematical, and the
Vital-Fluid Schools; and finally of the Psychical School,
who hold the Vital Powers to be derived from the Soul
(_Psyche_).
{{174}}
CHAPTER II.
SUCCESSIVE BIOLOGICAL HYPOTHESES.
SECT. I.--_The Mystical School._
IN order to abbreviate as much as can conveniently be done
the historical view which I have now to take, I shall
altogether pass over the physiological speculations of the
ancients, and begin my survey with the general revival of
science in modern times.
We need not dwell long on the fantastical and unsubstantial
doctrines concerning physiology which prevailed in the
sixteenth century, and which flowed in a great measure from
the fertile but ill-regulated imaginations of the
cultivators of Alchemy and Magic. One of the prominent
doctors of this school is the celebrated Paracelsus, whose
doctrines contained a combination of biblical
interpretations, visionary religious notions, fanciful
analogies, and bold experiments in practical medicine. The
opinion of a close but mystical resemblance of parts between
the universe and the human body,--the _Macrocosm_ and the
_Microcosm_,--as these two things, thus compared, were
termed, had probably come down from the Neoplatonists; it
was adopted by the Paracelsists[1\9], and connected with
various astrological dreams and cabbalistic riddles. A
succession of later Paracelsists[2\9], Rosicrucians, and
other fanatics of the same kind, continued into the
seventeenth century. Upon their notions was founded the
pretension of curing wounds by a sympathetic powder, which
Sir Kenelm Digby, among others, asserted; while animal
magnetism, and the transfer of diseases from one person to
another[3\9], were maintained by others of this {175}
school. They held, too, the doctrines of _astral bodies_
corresponding to each terrestrial body; and of the
_signatures_ of plants, that is, certain features in their
external form by which their virtues might be known. How
little advantage or progress real physiology could derive
from speculations of this kind may be seen from this, that
their tendency was to obliterate the distinction between
living and lifeless things: according to Paracelsus, all
things are alive, eat, drink, and excrete; even minerals and
fluids[4\9]. According to him and his school, besides
material and immaterial beings, there are _elementary
Spirit_s which hold an intermediate place, _Sylvans_,
_Nymphs_, _Gnomes_, _Salamanders_, &c. by whose agency
various processes of enchantment may be achieved, and things
apparently supernatural explained. Thus this spiritualist
scheme dealt with a world of its own by means of fanciful
inventions and mystical visions, instead of making any step
in the study of nature.
[Note 1\9: Spr. iii. 456.]
[Note 2\9: _Ib._ iv. 270.]
[Note 3\9: _Ib._ iv. 276.]
[Note 4\9: Spr. iii. 458. Parac. _De Vita Rerum Naturalium_, p. 889.]
Perhaps, however, one of the most fantastical of the
inventions of Paracelsus may be considered as indicating a
perception of a peculiar character in the vital powers.
According to him, the business of digestion is performed by
a certain demon whom he calls _Archæus_, who has his abode
in the stomach, and who, by means of his alchemical
processes, separates the nutritive from the harmful part of
our food, and makes it capable of assimilation[5\9]. This
fanciful notion was afterwards adopted and expanded by Van
Helmont[6\9]. According to him the stomach and spleen are
both under the direction of this Master-spirit, and these
two organs form a sort of _Duumvirate_ in the body.
[Note 5\9: _Ib._ iii. 468.]
[Note 6\9: _Ib._ iv. 302.]
But though we may see in such writers occasional gleams of
physiological thought, the absence of definite physical
relations in the speculations thus promulgated was
necessarily intolerable to men of sound understanding and
scientific tendencies. Such men naturally took hold of that
part of the phenomena of life which could be most distinctly
conceived, and {176} which could be apparently explained by
means of the sciences then cultivated; and this was the part
which appeared to be reducible to chemical conceptions and
doctrines. It will readily be supposed that the processes of
chemistry have a considerable bearing upon physiological
processes, and might, till their range was limited by a
sound investigation, be supposed to have still more than
they really had; and thus a Physiology was formed which
depended mainly upon Chemistry, and the school which held
this doctrine has been called the _Iatrochemical_ School.
SECT. II.--_The Iatrochemical School._
That all physical properties, and therefore chemical
relations, have a material influence on physiological
results, was already recognized, though dimly, in the
Galenic doctrine of the 'four elementary qualities.' But at
the time of Paracelsus, chemical action was more distinctly
than before separated from other kinds of physical action;
and therefore a physiological doctrine, founded upon
chemistry, and freed from the extravagance and mysticism of
the Paracelsists, was a very promising path of speculation.
Andrew Libavius[7\9] of Halle, in Saxony, Physician and
Teacher in the Gymnasium at Koberg, is pointed out by
Sprengel as the person who began to cultivate chemistry, as
distinct from the theosophic fantasies of his predecessors;
and Angelus Sala of Vienna[8\9], as his successor. The
latter has the laudable distinction of having rejected the
prevalent conceits about a potable gold, a universal
medicine, and the like[9\9]. In Germany already at the
beginning of the seventeenth century a peculiar chair of
_Chymiatria_ was already created at Marpurg: and many in
various places pursued the same studies, till, in the middle
of the seventeenth century, we come to Lemery[10\9], the
principal reformer of pharmaceutical chemistry. But we are
not here so much concerned {177} with the practical as with
the theoretical parts of Iatrochemistry; and hence we pass
on to Sylvius[11\9] and his system.
[Note 7\9: Spr. iii. 550.]
[Note 8\9: _Ib._ iv. 281.]
[Note 9\9: _Ib._ iv. 283.]
[Note 10\9: _Ib._ iv. 291.]
[Note 11\9: Spr. iv. 336.]
The opinion that chemistry had an important bearing upon
physiology did not, however, begin with Sylvius. Paracelsus,
among his extravagant absurdities, did some service to
medicine by drawing attention to this important truth. He
used[12\9] chemical principles for the explanation of
particular diseases: most or all diseases according to him,
arise from the effervescence of salts, from the combustion
of sulphur, or from the coagulation of mercury. His
medicines were chemical preparations; and it was[13\9] an
undeniable advantage of the Paracelsian doctrine that
chemistry thus became indispensable to the physician. We
still retain a remnant of the chemical nomenclature of
Paracelsus in the term _tartar_, denoting the stony
concretion which forms on the teeth[14\9]. According to him
there is a certain substance, the basis of all diseases
which arise from a thickening of the juices and a collection
of earthy matter; and this substance he calls _Tartarus_,
because 'it burns like the fire of hell.' Helmont, the
successor of Paracelsus in many absurdities, also followed
him in the attempt to give a chemical account, however loose
and wild, of the functions of the human body; and is by
Sprengel considered, with all his extravagancies, as a
meritorious and important discoverer. The notion of the
fermentation of fluids[15\9], and of the aërial product
thence resulting, to which he gave the name of _Gas_, forms
an important part of his doctrines; and of the six
digestions which he assumes, the _first_ prepares an acid,
which is neutralized by the gall when it reaches the
duodenum, and this constitutes the _second_ digestion.
[Note 12\9: _Ib._ iii. 472.]
[Note 13\9: _Ib._ iii. 482.]
[Note 14\9: _Ib._ iii. 475.]
[Note 15\9: Vol. v. 315.]
I have already, in the History of Chemistry[16\9], stated,
that the doctrine of the opposition of acid and alkali, the
great step which theoretical chemistry owes to Sylvius, was
first brought into view as a physiological {178} tenet,
although we had then to trace its consequences in another
science. The explanation of all the functions of the animal
system, both healthy and morbid, by means of this and other
chemical doctrines, and the prescription of methods of cure
founded upon such explanations, form the scheme of the
_iatrochemical_ school; a school which almost engrossed the
favour of European physicians during the greater part of the
seventeenth century.
[Note 16\9: _Hist. Ind. Sc._ b. xiii. c. 2.]
Sylvius taught medicine at Leyden, from the year 1658, with
so much success, that Boerhaave alone surpassed him[17\9].
His notions, although he piqued himself on their
originality, were manifestly suggested in no small degree
(as all such supposed novelties are) by the speculations of
his predecessors, and the spirit of the times. Like
Helmont[18\9], he considers digestion as consisting in a
fermentation; but he states it more definitely as the
effervescence of an acid, supplied by the saliva and the
pancreatic juice, with the alkali of the gall. By various
other hypothetical processes, all of a chemical nature, the
blood becomes a collection of various juices, which are the
subjects of the speculations of the iatrochemists, to the
entire neglect of the solid parts of the body. Diseases were
accounted for by a supposed prevalence of one or the other
of the acrid principles, the acid or the alkaline: and
Sylvius[19\9] was bold enough to found upon these hypotheses
practical methods of cure, which were in the highest degree
mischievous.
[Note 17\9: Spr. iv. 336.]
[Note 18\9: _Ib._ 338.]
[Note 19\9: _Ib._ iv. 345.]
The Sylvian doctrine was often combined with some of the
notions of the Cartesian system of philosophy; but this
mixture I shall not notice, since my present object is to
trace the history of a mere chemical physiology as one of
the unsuccessful attempts at a philosophy of life. With
various modifications, this doctrine was diffused over
Europe. It gave rise to several controversies, which turned
upon the questions of the novelty of the doctrine, and the
use of chemical remedies to which it pointed, as well as
upon its {179} theoretical truth. We need not dwell long
upon these controversies, although they were carried on with
no small vehemence in their time. Thus the school of Paris
opposed all innovation, remained true to the Galenic
dogmatism, and declared itself earnestly against all
combination of chemistry with medicine; and even against the
chemical preparation of medicaments. Guy Patin, a celebrated
and learned professor of that day, declares[20\9] that the
chemists are no better than forgers, and ought to be
punished as such. The use of antimonial medicines was a main
point of dispute between the iatrochemists and their
opponents; Patin maintained that more men had been destroyed
by antimony than by the thirty years' war of Germany; and
endeavoured to substantiate this assertion by collecting all
such cases in his _Martyrologium Antimonii_. It must have
been a severe blow to Patin when[21\9] in 1666, the Doctors
of the Faculty of Paris, assembled by command of the
parliament, declared, by a majority of ninety-two voices,
that the use of antimonial medicines was allowable and
laudable, and when all attempts to set aside this decision failed.
[Note 20\9: Spr. 349.]
[Note 21\9: _Ib._ iv. 350.]
Florentius Schuyl of Leyden sought to recommend the
iatrochemical doctrines, by maintaining that they were to be
found in the Hippocratic writings; nor was it difficult to
give a chemical interpretation of the humoral pathology of
the ancients. The Italian[22\9] physicians also, for the
most part, took this line, and attempted to show the
agreement of the principles of the ancient school of
medicine with the new chemical notions. This, indeed, is the
usual manner in which the diffusion of new theoretical ideas
becomes universal.
[Note 22\9: _Ib._ 368.]
The progress of the chemical school of medicine in
England[23\9] requires our more especial notice. Willis was
the most celebrated champion of this sect. He assumed, but
with modifications of his own, the three Paracelsian
principles, Salt, Sulphur, and Mercury; considered digestion
as the effect of an acid, and {180} explained other parts of
the animal economy by distillation, fermentation, and the
like. All diseases arise from the want of the requisite
_ferment_; and the physician, he says[24\9], may be compared
to a vintner, since both the one and the other have to take
care that the necessary fermentations go on, that no foreign
matter mixes itself with the wine of life, to interrupt or
derange those operations. In the middle of the seventeenth
century, medicine had reached a point in which the life of
the animal body was considered as merely a chemical process;
the wish to explain everything on known principles left no
recognized difference between organized and unorganized
bodies, and diseases were treated according to this delusive
notion. The condition of chemistry itself during this
period, though not one of brilliant progress, was
sufficiently stable and flourishing to give a plausibility
to any speculation which was founded on chemical principles;
and the real influence of these principles in the animal
frame could not be denied.
[Note 23\9: _Ib._ 353.]
[Note 24\9: Spr. 354.]
The iatrochemists were at first resisted, as we have seen,
by the adherents of the ancient schools; they were attacked
on various grounds, and finally deposed from them ascendancy
by another sect, which we have to speak of, as the
iatromathematical, or mechanical school. This sect was no
less unsatisfactory and erroneous in its positive doctrines
than the chemists had been; for the animal frame is no more
a mere machine than a mere laboratory: but it promoted the
cause of truth, by detecting and exposing the insufficient
explanations and unproved assertions of the reigning theory.
Boyle was one of the persons who first raised doubts against
the current chemical doctrines of his time, as we have
elsewhere noted; but his objections had no peculiar
physiological import. Herman Coming[25\9], the most learned
physician of his time, a contemporary with Sylvius, took a
view more pertinent to our present object; for he not only
rejected the alchemical {181} and hermetical medicines, but
taught expressly that chemistry, in its then existing
condition, was better fitted to be of use in the practice of
pharmacy, than in the theories of physiology and pathology.
He made the important assertion, also, that chemical
principles do not pre-exist _as such_ in the animal body;
and that there are higher powers which operate in the
organic world, and which do not depend on the form and
mixture of matter.
[Note 25\9: _Ib._ iv. 361.]
Attempts were made to prove the acid and alkaline nature of
the fluids of the human body by means of experiments, as by
John Viridet of Geneva[26\9], and by Raimond
Vieussens[27\9], the latter of whom maintained that he had
extracted an acid from the blood, and detected a ferment in
the stomach. In opposition to him, Hecquet, a disciple of
the iatromathematical school, endeavoured to prove that
digestion was performed, not by means of fermentation, but
by trituration. Hecquet's own opinions cannot be defended;
but his objections to the chemical doctrines, and his
assertion of the difference of chemical and organical
processes, are evidences of just thought[28\9].
[Note 26\9: Spr. iv. 329.]
[Note 27\9: _Ib._ 350, (1715).]
[Note 28\9: _Ib._ 401.]
The most important opponents of the iatrochemical school
were Pitcairn in England, Bohn and Hoffman in Germany, and
Boerhaave in Holland. These eminent physicians, about the
end of the seventeenth century, argued on the same grounds
of observation, that digestion is not fermentation, and that
the Sylvian accounts of the origin of diseases by means of
acid and alkali are false. The arguments and authority of
these and other persons finally gained an ascendancy in the
medical world, and soon after this period we may consider
the reign of the chemical school of physiology as past. In
fact, the attempts to prove its assertions experimentally
were of the feeblest kind, and it had no solid basis on
which it could rest, so as to resist the shock of the next
hypothesis which the progress of the physical sciences might
impel against it. We may, therefore, now consider the
opinion of the mere {182} chemical nature of the vital
processes as disproved, and we proceed next to notice the
history of another unsuccessful essay to reduce vital
actions to known actions of another kind.
SECT. III.--_The Iatromathematical School._
In the first Section of this chapter, we enumerated the
biological hypotheses which at first present themselves, as
the mystical, the mechanical, the chemical. We might have
expected that they should occur to men's minds in the order
thus stated: and in fact they did so; for the physiology of
the ancient materialists, as Democritus and Lucretius, is
mechanical so far as it is at all distinct in its views, and
thus the mechanical preceded the chemical doctrine. But in
modern times, the fluid or chemical physiology was developed
before the solid or mechanical: of which the reason appears
to have been this;--that Mechanics and Chemistry began to
assume a scientific character about the same time; and that
of the two, Chemistry not only appeared at first sight more
applicable to the functions of the body, because all the
more rapid changes appear to be connected with modifications
of the fluids of the animal system, but also, by its wider
range of facts and more indefinite principles, afforded a
better temporary refuge for the mind when perplexed by the
difficulties and mysteries which spring out of the
speculations concerning life. But if Chemistry was thus at
first a more inviting field for the physiologist, Mechanics
soon became more attractive in virtue of the splendid
results obtained by the schools of Galileo and Newton. And
when the insufficiency of chemical physiology was discovered
by trial, as we have seen it was, the hope naturally arose,
that the mechanical principles which had explained so many
of the phenomena of the external universe might also be
found, applicable to the smaller world of material
life;--that the _microcosm_ as well as the _macrocosm_ might
have its mechanical principles. From this hope sprung the
{183} Iatromathematical School, or school of Mechanical
Physiologists.
We may, however, divide this school into two parts, the
Italian, and the Cartesio-Newtonian sect. The former
employed themselves in calculating and analysing a number of
the properties of the animal frame which are undoubtedly
mechanical; the latter, somewhat intoxicated by the supposed
triumphs of the corpuscular philosophy, endeavoured to
extend these to physiology, and for this purpose introduced
into the subject many arbitrary and baseless hypotheses. I
will very briefly mention some of the writers of both these sects.
The main points to which the Italian or genuine Mechanical
Physiologists attended, were the application of mechanical
calculations to the force of the muscles, and of hydraulical
reasonings to the motion of the fluids of the animal system.
The success with which Galileo and his disciples had pursued
these branches of mechanical philosophy, and the ascendancy
which they had obtained, first in Italy, and then in other
lands, made such speculations highly interesting. Borelli
may be considered as the first great name in his line, and
his book, _De Motu Animalium_, (_Opus Posthumum_, Romæ,
1680,) is even now a very instructive treatise on the forces
and action of the bones and muscles. This, certainly one of
the most valuable portions of mechanical physiology, has not
even yet been so fully developed as it deserves, although
John Bernoulli[29\9] and his son Daniel[30\9] applied to it
the resources of analysis, and Pemberton[31\9] in England,
pursued the same subject. Other of these mechanico-physiological
problems consisted in referring the pressure of the blood
and of the breath to hydrostatical principles. In this
manner Borelli was led to assert that the muscles of the
heart exert a force of 180,000 pounds[32\9]. But a little
later, Keill reduced this force {184} to a few ounces[33\9].
Keill and others attempted to determine, on similar
principles, the velocity of the blood; we need not notice
the controversies which thus arose, since there is not
involved in them any peculiar physiological principle.
[Note 29\9: _De Motu Musculorum_.]
[Note 30\9: _Act. Acad. Petrop._]
[Note 31\9: _Course of Physiology_, 1773.]
[Note 32\9: Spr. iv. 110.]
[Note 33\9: Spr. iv. 443.]
The peculiar character of the iatromathematical school, as
an attempt at physiological theory, is more manifest in its
other section, which we have called the Cartesio-Newtonian.
The Cartesian system pretended to account for the
appearances and changes of bodies by means of the size,
figure, and motion of their minute particles. And though
this system in its progress towards the intellectual empire
of Europe was suddenly overturned by the rise of the
Newtonian philosophy, these corpuscular doctrines rather
gained than lost by the revolution; for the Newtonian
philosophy enlarged the powers of the corpuscular
hypothesis, by adding the effects of the attractive and
repulsive forces of particles to those of their form and
motion. By this means, although Newton's discoveries did not
in fact augment the probability of the corpuscular
hypothesis, they so far increased its plausibility, that
this hypothesis found favour both with Newton himself and
his contemporaries, no less than it had done with the
Cartesians.
The attempt to apply this corpuscular hypothesis to
physiology was made by Des Cartes himself. The general
character of such speculations may easily be guessed[34\9].
The secretions are effected by the organs operating after
the manner of sieves. Bound particles pass through
cylindrical tubes, pyramidal ones through triangular pores,
cubical particles through square apertures, and thus
different kinds of matter are separated. Similar
speculations were pursued by other mathematicians: the
various diameter of the vessels[35\9], their curvatures,
folds, and angles, were made subjects of calculation.
Bellini, Donzellini, Gulielmini, in Italy; Perrault, Dodart,
in France; Cole, Keill, Jurin, in England, were the
principal cultivators of such studies. {185} In the earlier
part of the eighteenth century, physiological theorists
considered it as almost self-evident that their science
required them to reason concerning the size and shape of the
particles of the fluids, the diameter and form of the
invisible vessels. Such was, for instance, the opinion of
Cheyne[36\9], who held that acute fevers arise from the
obstruction of the glands, which occasions a more vehement
motion of the blood. Mead, the physician of the King, and
the friend of Newton, in like manner explained the effects
of poisons by hypotheses concerning the form of their
particles[37\9], as we have already seen in speaking of chemistry.
[Note 34\9: _Ib._ 329.]
[Note 35\9: _Ib._ 432.]
[Note 36\9: Spr. iv. 223.]
[Note 37\9: _ Mechanical Account of Poisons_, 1702.]
It is not necessary for us to dwell longer on this subject,
or to point out the total insufficiency of the mere
mechanical physiology. The iatrochemists had neglected the
effect of the solids of the living frame; the
iatromathematicians attended only to these[38\9]. And even
these were considered only as canals, as cords, as levers,
as lifeless machines. These reasoners never looked for any
powers of a higher order than the cohesion, the resistance,
the gravity, the attraction, which operate in inert matter.
If the chemical school assimilated the physician to a
vintner or brewer, the mechanical physiologists made him an
hydraulic engineer; and, in fact, several of the
iatromathematicians were at the same time teachers of
engineering and of medicine.
[Note 38\9: Spr. iv. 419.]
Several of the reasoners of this school combined chemical
with their mechanical principles; but it would throw no
additional light upon the subject to give any account of
these, and I shall therefore go on to speak of the next form
of the attempt to explain the processes of life.
SECT. IV.--_The Vital-Fluid School._
I speak here, not of that opinion which assumes some kind of
fluid or ether as the means of {186} communication along the
_nerves_ in particular, but of the hypothesis that _all_ the
peculiar functions of _life_ depend upon some subtile
ethereal substance diffused through the frame;--not of a
_Nervous_ Fluid, but of a _Vital_ Fluid. Again, I
distinguish this opinion from the doctrine of an
_immaterial_ vital power or principle, an Animal Soul, which
will be the subject of the next Section: nor is this
distinction insignificant; for a material element, however
subtile, however much spiritualized, must still act
everywhere according to the same laws; whereas we do not
conceive an immaterial spirit or soul to be subject to this
necessity.
The iatromathematical school could explain to their own
satisfaction how motions, once begun, were transferred and
modified; but in many organs of the living frame there
seemed to be a power of beginning motion, which is beyond
all mere mechanical action. This led to the assumption of a
Principle of a higher kind, though still material. Such a
Principle was asserted by Frederick Hoffmann, who was born
at Halle, in 1660[39\9], and became Professor of Medicine at
the newly established University there in 1694. According to
him[40\9], the reason of the greater activity of organized
bodies lies in the influence of a material substance of
extreme subtilty, volatility, and energy. This is, he holds,
no other than the Ether, which, diffused through all nature,
produces in plants the bud, the secretion and motion of the
juices, and is separated from the blood and lodged in the
brain of animals[41\9]. From this, acting through the
nerves, must be derived all the actions of the organs in the
animal frame; for when the influence of the nerve upon the
muscle ceases, muscular motion ceases also.
[Note 39\9: Spr. v. 254.]
[Note 40\9: _Ib._ v. 257.]
[Note 41\9: _De Differentiâ Organismi et Mechanismi_, pp. 48, 67.]
The mode of operation of this vital fluid was, however, by
no means steadily apprehended by Hoffmann and his followers.
Its operations are so far mechanical[42\9] that all effects
are reduced to motion, yet they {187} cannot be explained
according to known mechanical laws. At one time the effects
are said to take place according to laws of a Higher
Mechanics which are still to be discovered[43\9]. At another
time, in complete contradiction of the general spirit of the
system, metaphysical conceptions are introduced: each
particle of the vital fluid is said to have a determined
_idea_ of the whole mechanism and organism[44\9], and
according to this, it forms the body and preserves it by its
motion. By means of this fluid the soul operates upon the
body, and the instincts and the passions have their source
in this material sensitive soul. This attribution of ideas
to the particles of the fluid is less unaccountable when we
recollect that something of the same kind is admitted into
Leibnitz's system, whose Monads have also ideas.
[Note 42\9: Spr. v. 262, 3.]
[Note 43\9: Hoffmann, _Opp._ Vol. v. p. 123.]
[Note 44\9: _De Diff. Organ. et Mechan._ p. 81.]
Notwithstanding its inconsistencies, Hoffmann's system was
received with very general favour both in Germany and in the
rest of Europe; the more so, inasmuch as it fell in very
well with the philosophy both of Leibnitz and of Newton. The
Newtonians were generally inclined to identify the Vital
Fluid with the Ether, of which their master was so strongly
disposed to assume the existence: and indeed he himself
suggested this identification.
When the discoveries made respecting Electricity in the
course of the eighteenth century had familiarized men with
the notion of a pervading subtile agent, invisible,
intangible, yet producing very powerful effects in every
part of nature, physiologists also caught at the suggestion
of such an agent, and tried, by borrowing or imitating it,
to aid the imperfection of their notions of the vital
powers. The Vital Principle[45\9] was imagined to be a
substance of the same kind, by some to be the same
substance, with the Electric Fluid. By its agency all these
processes in organized bodies were accounted for which
cannot be {188} explained by mechanical or chemical laws, as
the secretion of various matters (tears, milk, bile, &c.)
from an homogeneous fluid, the blood; the production of
animal heat, digestion, and the like. According to John
Hunter, this attenuated substance pervaded the blood itself,
as well as the solid organic frame; and the changes which
take place in the blood which has flowed out of the veins
into a basin are explained by saying that it is, for a time,
till this vital fluid evaporates, truly alive.
[Note 45\9: Prichard, _On the Doctrine of a Vital
Principle_, p. 12.]
The notion of a Vital Fluid appears also to be favourably
looked upon by Cuvier; although with him this doctrine is
mainly put forwards in the form of a Nervous Fluid. Yet in
the following passage he extends the operation of such an
agent to all the vital functions[46\9]: 'We have only to
suppose that all the medullary and nervous parts produce the
Nervous Agent, and that they alone conduct it; that is, that
it can only be transmitted by them, and that it is changed
or consumed by their actions. Then everything appears
simple. A detached portion of muscle preserves for some time
its irritability, on account of the portion of nerve which
always adheres to it. The sensibility and the irritability
reciprocally exhaust each other by their exercise, because
they change or consume the same agent. All the interior
motions of digestion, secretion, excretion, participate in
this exhaustion, or may produce it. All local excitation of
the nerves brings thither more blood by augmenting the
irritability of the arteries, and the afflux of blood
augments the real sensibility by augmenting the production
of the nervous agent. Hence the pleasures of titillations,
the pains of inflammation. The particular sensations
increase in the same manner and by the same causes; and the
imagination exercises, (still by means of the nerves,) upon
the internal fibres of the arteries or other parts, and
through them on the sensations, an action analogous to that
of the will upon the voluntary motions. As each exterior
sense is exclusively disposed {189} to admit the substances
which it is to perceive, so each interior organ, secretory
or other, is also more excitable by some one agent than by
another: and hence arises what has been called the _proper
sensibility_ or _proper life of the organs_; and the
influence of specifics which, introduced into the general
circulation, affect only certain parts. In fine, if the
nervous agent cannot become sensible to us, the reason is
that all sensation requires that this agent should be
altered in some way or other; and it cannot alter itself.
[Note 46\9: _Hist. Sc. Nat. depuis_ 1789, i. 214.]
'Such is the summary idea which we may at present form of
the mutual and general working of the vital powers in
animals.'
Against the doctrine of a Vital Fluid as one uniform
material agent pervading the organic frame, an argument has
been stated which points out extremely well the
philosophical objection to such an hypothesis[47\9]. If the
Vital Principle be the _same_ in all parts of the body, how
does it happen, it is asked, that the secretions are so
_different_? How do the particles in the blood, separated
from their old compounds and united into new ones, under the
same influence, give origin to all the different fluids
which are produced by the glands? The liver secretes bile,
the lacrymal gland, tears, and so on. Is the Vital Principle
different in all these organs? To assert this, is to
multiply nominal principles without limit, and without any
advance in the explanation of facts. Is the Vital Principle
the same, but its operation modified by the structure of the
organ? We have then two unknown causes, the Vital Principle
and the Organic Structure, to account, for the effect. By
such a multiplication of hypotheses nothing is gained. We
may as well say at once, that the structure of the organ,
acting by laws yet unknown, is the cause of the peculiar
secretion. It is as easy to imagine this structure acting to
produce the whole effect, as it is to imagine it modifying
the activity of another agent. Thus the hypothesis of the
Vital Fluid in this form explains nothing, and does not in
any {190} way help onwards the progress of real biological
knowledge.
[Note 47\9: Prichard, _On a Vital Principle_, p. 98.]
The hypothesis of an _immaterial_ vital principle must now be
considered.
SECT. V.--_The Psychical School._
The doctrine of an Animal Soul as the principle which makes
the operations of organic different from those of inorganic
matter, is quite distinct from, and we may say independent
of, the doctrine of the soul as the intelligent, moral,
responsible part of man's nature. It is the former doctrine
alone of which we have here to speak, and those who thus
hold the existence of an immaterial agent as the cause of
the phenomena of life, I term the _Psychical School_.
Such a view of the constitution of living things is very
ancient. For instance, Aristotle's Treatise '_On the Soul_,'
goes entirely upon the supposition that the Soul is the
cause of motion, and he arrives at the conclusion that there
are different _parts_ in the Soul; the _nutritive_ or
_vegetative_, the _sensitive_, and the _rational_[48\9].
[Note 48\9: Aristotle. Περὶ Ψυχῆς, ii. 2.]
But this doctrine is more instructive to us, when it appears
as the antagonist of other opinions concerning the nature of
life. In this form it comes before us as promulgated by
Stahl, whom we have already noticed as one of the great
discoverers in chemistry. Born in the same year as Hoffmann,
and appointed at his suggestion professor at the same time
in the same new university of Halle, he soon published a
rival physiological theory. In a letter to Lucas Schröck,
the president of the Academy of Naturalists, he describes
the manner in which he was led to form a system for
himself[49\9]. Educated in the tenets of Sylvius and Willis,
according to which all diseases are derived from the acidity
of the fluids, Stahl, when a young student, often wondered
how these fluids, so liable to be polluted and corrupted,
are so wonderfully preserved through innumerable external
influences, and seem to {191} be far less affected by these
than by age, constitution, passion. No material cause could,
he thought, produce such effects. No attention to mechanism
or chemistry alone could teach us the true nature and laws
of organization.
[Note 49\9: Spr. v. 303.]
So far as Stahl recognized the influence, in living bodies,
of something beyond the range of mechanics and chemistry,
there can be no doubt of the sound philosophy of his views;
but when he proceeds to found a positive system of
physiology, his tenets become more precarious. The basis of
his theory is this[50\9]: the body has, as body, no power to
move itself, and must always be put in motion by immaterial
substances. All motion is a spiritual act[51\9]. The source
of all activity in the organic body, from which its
preservation, the permanency of its composition, and all its
other functions proceed, is an immaterial being, which Stahl
calls the _Soul_; because, as he says, when the effects are
so similar, he will not multiply powers without necessity.
Of this principle, he says, as the Hippocratians said of
Nature, that 'it does without teaching what it ought to
do[52\9],' and does it 'without consideration[53\9].' These
ancient tenets Stahl interprets in such a manner that even
the involuntary motions proceed from the soul, though
without reflection or clear consciousness. It is indeed
evident, that there are many customary motions and
sensations which are perfectly rational, yet not the objects
of distinct consciousness: and thus instinctive motions, and
those of which we are quite unconscious, may still be
connected with reason. The questions which in this view
offer themselves, as, how the soul passes from the mother to
the child, he dismisses as unprofitable[54\9]. He considers
nutrition and secretion as the work of the soul. The
corpuscular theory and the doctrine of animal spirits {192}
are, he rightly observes, mere hypotheses, which are
arbitrary in their character, and only shift the difficulty.
For, if the animal spirits are not matter, how can they
explain the action of an immaterial substance on the body;
and if they are matter, how are they themselves acted on?
[Note 50\9: Spr. v. 308]
[Note 51\9: _Ib._ v. 314.]
[Note 52\9: Stahl, περὶ φύσεως ἀπαίδευτου.]
[Note 53\9: οὐκ ἐκ διανοίης.]
[Note 54\9: This was of course an obvious problem. Harvey,
_On Generation_ Exercise 27, p. 148, teaches, 'That the egg
is not the production of the womb, but of the soul.']
This doctrine of the action of the soul on the body, was
accepted by many persons, especially by the
iatromathematicians, who could not but feel the
insufficiency of their system without some such supplement:
such were Cheyne and Mead. In Germany, Stahl's disciples in
physiology were for the most part inconsiderable
persons[55\9]. Several Englishmen who speculated concerning
the metaphysics as well as the physiology of Sensation and
Motion, inclined to this psychical view, as Porterfield and
Whytt. Among the French, Boissier de Sauvages was the most
zealous defender of the Stahlian system. Actions, he
says[56\9], which belong to the preservation of life are
determined by a moral not a mechanical necessity. They
proceed from the soul, but cannot be controlled by it, as
the starting from fear, or the trembling at danger. Unzer, a
physician at Altona[57\9], was also a philosophical
Stahlian[58\9].
[Note 55\9: Spr. v. 339, &c.]
[Note 56\9: _Ib._ 358.]
[Note 57\9: A.D. 1799]
[Note 58\9: Spr. v. 360.]
We need not dwell on the opposition which was offered to
this theory, first by Hoffmann, and afterwards by Haller.
The former of these had promulgated, as we have seen, the
rival theory of a Nervous Fluid, the latter was the
principal assertor of the doctrine of Irritability, an
important theory on which we may afterwards have to touch.
Haller's animosity against the Stahlian hypothesis is a
remarkable feature in one who is in general so tolerant in
his judgment of opinions. His arguments are taken from the
absence of the control of the will over the vital actions,
from the want of consciousness accompanying these actions,
from the uniformity of them in different conditions of the
mind, and from the small sensibility of {193} the heart
which is the source of the vital actions. These objections,
and the too decided distinction which Haller made between
voluntary and involuntary muscles, were very satisfactorily
answered by Whytt and Platner. In particular it was urged
that the instinctive actions of brutes are inexplicable by
means of mechanism, and may be compared with the necessary
vital actions of the human body. Neither kind are
accidental, neither kind are voluntary, both are performed
without reflection.
Without tracing further the progress of the Psychical
Doctrine, I shall borrow a few reflections upon it from
Sprengel[59\9]:--
'When the opponents of the Stahlian system repeat
incessantly that the assumption of a psychical cause in
corporeal effects is a metaphysical speculation which does
not belong to medicine, they talk to no purpose. The states
of the soul are objects of our internal experience, and
interest the physician too nearly to allow him to neglect
them. The innumerable unconscious efforts of the soul, the
powerful and daily effects of the passions upon the body,
too often put to confusion those who would expel into the
region of metaphysics the dispositions of the mind. The
connexion of our knowledge of the soul, as gathered from
experience, with our knowledge of the human body, is far
closer than the mechanical and chemical physiologists
suspect.
[Note 59\9: Spr. v. 383.]
'The strongest objection against the psychical system, and
one which has never been sufficiently answered by any of its
advocates, is the universality of organic effects in the
_vegetable_ kingdom. The comparison of the physiology of
plants with the physiology of animals puts the latter in its
true light. Without absolutely trifling with the word
_soul_, we cannot possibly derive from a soul the organic
operations of vegetables. But just as little can we, as some
Stahlians have done, draw a sharp line between plants and
animals, and ascribe the processes of the former to mere
mechanism, while {194} we derive the operations of the
latter from an intellectual principle. Not to mention that
such a line is not possible, the rise of the sap and the
alteration of the fluids of plants cannot be derived
entirely from material causes as their highest origin.'
Thus, I may add, this psychical theory, however difficult to
defend in its detail, does in its generalities express some
important truths respecting the vital powers. It not only,
like the last theory, gives unity to the living body, but it
marks, more clearly than any other theory, the wide interval
which separates mechanical and chemical from vital action,
and fixes our attention upon the new powers which the
consideration of life compels us to assume. It not only
reminds us that these powers are elevated above the known
laws of the material world, but also that they are closely
connected with the world of thought and feeling, of will and
reason; and thus it carries us, in a manner in which none of
the preceding theories have done, to a true conception of a
living, conscious, sentient, active individual.
At the same time we cannot but allow that the life of
plants and of the lower orders of animals shows us very
clearly that, in order to arrive at any sound and consistent
knowledge respecting life, we must form some conception of
it from which all the higher attributes which the term
'soul' involves, are utterly and carefully excluded; and
therefore we cannot but come to the conclusion that the
psychical school are right mainly in this; that in ascribing
the functions of life to a _soul_, they mark strongly and
justly the impossibility of ascribing them to any known
attributes of _body_.
{{195}}
CHAPTER III.
ATTEMPTS TO ANALYSE THE IDEA OF LIFE.
1. _Definitions of Life._--WE have seen in the preceding
chapter that all attempts to obtain a distinct conception of
the nature of Life in general have ended in failure, and
produced nothing beyond a negative result. And the
conjecture may now naturally occur, that the cause of this
failure resides in an erroneous mode of propounding to
ourselves the problem. Instead of contemplating Life as a
single Idea, it may perhaps be proper to separate it into
several component notions: instead of seeking for one cause
of all vital operations, it may be well to look at the
separate vital functions, and to seek their causes. When the
view of this possibility opens upon us, how shall we
endeavour to verify it, and to take advantage of it?
Let us, as one obvious course, take some of the attempts
which have been made to _define_ Life, and let us see
whether they appear to offer to us any analysis of the idea
into component parts. Such definitions, when they proceed
from men of philosophical minds, are the ultimate result of
a long course of thought and observation; and by no means
deserve to be slighted as arbitrary selections of
conditions, or empty forms of words.
2. Life has been defined by Stahl[60\9], 'The condition by
which a body resists a natural tendency to chemical changes,
such as putrefaction.' In like manner, M. von Humboldt[61\9]
defines living bodies to be 'those which, notwithstanding
the constant operation {196} of causes tending to change
their form, are hindered by a certain inward power from
undergoing such change.' The first of these definitions
amounts only to the assertion, that vital processes are not
chemical; a negative result, which we may accept as true,
but which is, as we have seen, a barren truth. The second
appears to be, in its import, identical with the first. An
_inward_ principle can only be understood as distinguished
from known external powers, such as mechanical and chemical
agencies. Or if, by an internal principle, we mean such a
principle as that of which we are _conscious_ within
ourselves, we ascribe a soul to all living things: an
hypothesis which we have seen is not more effective than the
former in promoting the progress of biological science.
Nearly the same criticism applies to such definitions as
that of Kant: that 'Life is an internal faculty producing
change, motion, and action.'
[Note 60\9: Treviranus, _Biologie_, p. 19. Stahlii, _**Theor.
Med._ p. 254.]
[Note 61\9: _Aphorismen aus d. Chem. Physiol. der Pflanzen_, s. 1.]
Other definitions refer us, not to some property residing in
the whole of an organized mass, but to the connexion and
relation of its parts. Thus M. von Humboldt[62\9] has given
another definition of a living body: that 'it is a whole
whose parts, arbitrarily separated, no longer resist
chemical changes.' But this additional assertion concerning
the parts, adds nothing of any value to the definition of
the whole. And in some of the lower kinds of plants and
animals it is hardly true as a fact.
[Note 62\9: _Versuche über die gereitzte Muskel und
Nervenfüser_, b. ii. p. 433.]
3. Another definition[63\9] places the character of Life in
'motions serviceable to the body moved.' To this it has been
objected[64\9], that, on this definition, the earth and the
planets are living bodies. Perhaps it would be more
philosophical to object to the introduction of so loose a
notion as that of a property being _serviceable_ to a body.
We might also add, that if we speak of all vital functions
as _motions_, we make an assumption quite unauthorized, and
probably false.
[Note 63\9: Erhard, Röschlaub's _Magazin der Heilkunde_, b.
i. st. 1. p. 69.]
[Note 64\9: Treviranus, _Biologie_, p. 41.]
{197} Other definitions refer the idea of Life to the idea
of Organization. 'Life is the activity of matter according
to laws of organization[65\9].' We are then naturally led to
ask, What is Organization? In reply to this is given us the
Kantian definition of Organization, which I have already
quoted elsewhere[66\9], 'An organized product of nature is
that in which all the parts are mutually ends and
means[67\9].' That this definition involves exact
fundamental ideas, and is capable of being made the basis of
sound knowledge, I shall hereafter endeavour to show. But I
may observe that such a definition leads us somewhat
further. If the parts of organized bodies are known to be
means to certain ends, this must be known because they
fulfil these ends, and produce certain effects by the
operation of a certain cause or causes. The question then
recurs, what is _the cause_ which produces such effects as
take place in organized or living bodies? and this is
identical with the problem of which in the last chapter we
traced the history, and related the failure of physiologists
in all attempts at its solution.
[Note 65\9: Schmid, _Physiologie_, b. ii. p. 274.]
[Note 66\9: _Hist. Ind. Sc._ b. xvii. c. viii. s. 2.]
[Note 67\9: Kant, _Urtheilskraft_, p. 296.]
4. But what has been just said suggests to us that it may be
an improvement to put our problem in another shape:--not to
take for granted that the cause of all vital processes is
one, but to suppose that there may be several separate
causes at work in a living body. If this be so, life is no
longer one kind of activity, but several. We have a number
of operations which are somehow bound together, and life is
the totality of all these: in short, life is not one
Function, but a System of Functions.
5. We are thus brought very near to the celebrated
definition of life given by Bichat[68\9]: 'Life is the sum
of the functions by which death is resisted.' But upon the
definition thus stated, we may venture to observe;--first,
that the introduction of the notion of {198} _death_ in
order to define the notion of _life_ appears to be
unphilosophical. We may more naturally define death with
reference to life, as the cessation of life; or at least we
may consider life and death as correlative and
interdependent notions. Again, the word 'sum,' used in the
way in which it here occurs, appears to be likely to convey
an erroneous conception, as if the functions here spoken of
were simply added to each other, and connected by
co-existence. It is plain that our idea of life involves
more than this: the functions are all clearly connected, and
mutually depend on each other; nutrition, circulation,
locomotion, reproduction,--each has its influence upon all
the others. These functions not merely co-exist, but exist
with many mutual relations and connexions; they are
continued so as to form, not merely a _sum_, but a _system_.
And thus we are led to modify Bichat's definition, and to
say that _Life is the system of vital functions_.
[Note 68\9: _Physiological Researches on Life and Death_.]
6. But it will be objected that by such a definition we
explain nothing: the notion of _vital functions_, it may be
said, involves the idea of _life_, and thus brings us round
again to our starting-point. Or if not, at least it is as
necessary to define Vital Functions as to define Life
itself, so that we have made little progress in our task.
To this we reply, that if any one seeks, upon such subjects,
some ultimate and independent definition from which he can,
by mere reasoning, deduce a series of conclusions, he seeks
that which cannot be found. In the Inductive Sciences, a
Definition does not form the basis of reasoning, _but points
out the course of investigation_. The definition must
include words; and the meaning of these words must be sought
in the progress and results of observations, as I have
elsewhere said[69\9]. 'The meaning of words is to be sought
in the progress of thought; the history of science is our
dictionary; the steps of scientific induction are our
definitions.' It will appear, I think, that it is more easy
for us to form an idea of a separate Function of the {199}
animal frame, as Nutrition or Reproduction, than to
comprehend Life in general under any single idea. And when
we say that Life is a system of Vital Functions, we are of
course directed to study these functions separately, and (as
in all other subjects of scientific research) to endeavour
to form of them such clear and definite ideas as may enable
us to discover their laws.
[Note 69\9: _Hist. Ind. Sc._ b. xiii. c. ix.]
7. The view to which we are thus led, of the most promising
mode of conducting the researches of Biology, is one which
the greatest and most philosophical physiologists of modern
times have adopted. Thus Cuvier considers this as the true
office of physiology at present. 'It belongs to modern
times,' he says, 'to form a just classification of the vital
phenomena; the task of the present time is to analyse the
forces which belong to each organic element, and upon the
zeal and activity which are given to this task, depends,
according to my judgment, the fortune of physiology[70\9].'
This classification of the phenomena of life involves, of
course, a distinction and arrangement of the vital
functions; and the investigation of the powers by which
these functions are carried on, is a natural sequel to such
a classification.
[Note 70\9: _Hist. Sc. Nat. dep._ 1789, i. 218.]
8. _Classification of Functions._--Attempts to classify the
Vital Functions of man were made at an early period, and
have been repeated in great number up to modern times. The
task of classification is exposed to the same difficulties,
and governed by the same conditions, in this as in other
subjects. Here, as in the case of other things, there may be
many classifications which are moderately good and natural,
but there is only one which is the best and the true natural
system. Here, as in other cases, one classification brings
into view one set of relations; another, another; and each
may be valuable for its special purpose. Here, as in other
cases, the classes may be well constituted, though the
boundary lines which divide them be somewhat indistinct, and
the order doubtful. Here, {200} as in other cases, we may
have approached to the natural classification without having
attained it; and here, as in other cases, to _define_ our
classes is the last and hardest of our problems.
9. The most ancient classification of the Functions of
living things[71\9], is the division of them into _Vital_,
_Natural_, and _Animal_. The Vital Functions are those which
cannot be interrupted without loss of life, as
_Circulation_, _Respiration_, and _Nervous Communication_.
The _Natural Functions_ are those which without the
intervention of the will operate on their proper occasions
to preserve the bodies of animals; they are _Digestion_,
_Absorption_, _Nutrition_; to which was added _Generation_.
The _Animal_ Functions are those which involve perception
and will, by which the animal is distinguished from the
vegetable; they are _Sensibility_, _Locomotion_, and _Voice_.
[Note 71\9: _Dict. des Sciences Nat._ art. _Fonctions_.]
The two great grounds of this division, the distinction of
functions which operate continually, and those which operate
occasionally; and again, the distinction of functions which
involve sensation and voluntary motion from those which do
not; are truly of fundamental importance, and gave a real
value to this classification. It was, however, liable to
obvious objections: namely, _First_, that the names of the
classes were ill chosen; for all the functions are natural,
all are vital: _Second_, that the lines of demarcation
between the classes are indefinite and ambiguous;
Respiration is a _vital_ function, as being continually
necessary to life; but it is also a _natural_ function,
since it occurs in the formation of the nutritive fluid, and
an _animal_ function, since it depends in part on the will.
But these objections were not fatal, for a classification
may be really sound and philosophical, though its boundary
lines are vague, and its nomenclature ill selected. The
division of the functions we have mentioned kept its ground
long; or was employed with a subdivision of one class, so as
to make them four; the _vital_, _natural_, _animal_ and
_sexual_ functions. {201}
10. I pass over many intermediate attempts to classify the
functions, and proceed to that of Bichat as that which is, I
believe, the one most generally assented to in modern times.
The leading principle in the scheme of this celebrated
physiologist is the distinction between _organic_ and
_animal_ life. This separation is nearly identical with the
one just noticed between the vital and animal functions; but
Bichat, by the contrasts which he pointed out between these
classes of functions, gave a decided prominence and
permanence to the distinction. The Organic Life, which in
animals is analogous to the life of vegetables, and the
Animal Life, which implies sensation and voluntary motion,
have each its system of organs. The center of the animal
life is the brain, of the organic life, the heart. The
former is carried on by a symmetrical, the latter, by an
unsymmetrical system of organs: the former produces
intermitting, the latter continuous actions: and, in
addition to these, other differences are pointed out. This
distinction of the two lives, being thus established, each
is subdivided into two orders of Functions. The Animal
Functions are passive, as _Sensation_: or active, as
_Locomotion_ and _Voice_; again, the Organic Functions are
those of Composition, which are concerned in taking matter
into the system; _Digestion_, _Absorption_, _Respiration_,
_Circulation_, _Assimilation_; and those of Decomposition,
which reject the materials when they have discharged their
office in the system; and these are again, _Absorption_,
_Circulation_, and _Secretion_. To these are added
_Calorification_, or the production of animal heat. It
appears, from what has been said, that _Absorption_ and
_Circulation_ (and we may add _Assimilation_ and
_Secretion_, which are difficult to separate,) belong alike
to the processes of composition and decomposition; nor in
truth, can we, with any rigour, separate the centripetal and
centrifugal movements in that vortex which, as we shall see,
is an apt image of organic life.
Several objections have been made to this classification:
and in particular, to the terms thus employed. It has been
asserted to be a perversion of language to {202} ascribe to
animals _two lives_, and to call the higher faculties in
man, perception and volition, the _animal_ functions. But,
as we have already said, when a classification is really
good, such objections, which bear only upon the mode in
which it is presented, are by no means fatal: and it is
generally acknowledged by all the most philosophical
cultivators of biology, that this arrangement of the
functions is better suited to the purposes of the science
than those which preceded it.
11. But according to the principles which we have already
laid down, the solidity of such a classification is to be
verified by its serving as a useful guide in biological
researches. If the arrangement which we have explained be
really founded in natural relations, it will be found that
in proportion as physiologists have studied the separate
functions above enumerated, their ideas of these functions,
and of the powers by which they are carried on, have become
more and more clear;--have tended more and more to the
character of exact and rigorous science.
To examine how far this has been the case with regard to all
the separate functions, would be to attempt to estimate the
value of all the principal physiological speculations of
modern times; a task far too vast and too arduous for any
one to undertake who has not devoted his life to such
studies. But it may properly come within the compass of our
present plan to show how, with regard to the broader lines
of the above classification, there has been such a progress
as we have above described, from more loose and inaccurate
notions of some of the vital functions to more definite and
precise ideas. This I shall attempt to point out in one or
two instances.
{{203}}
CHAPTER IV.
ATTEMPTS TO FORM IDEAS OF SEPARATE VITAL FORCES, AND FIRST
OF ASSIMILATION AND SECRETION.
SECT. I.--_Course of Biological Research._
1. IT is to be observed that at present I do not speak of
the progress of our knowledge with regard to the detail of
the processes which take place in the human body, but of the
approach made to some distinct Idea of the specially vital
part of each process. In the History of Physiology, it has
been seen[72\9] that all the great discoveries made respecting
the organs and motions of the animal frame have been
followed by speculations and hypotheses connected with such
discoveries. The discovery of the circulation of the blood
led to theories of animal heat; the discovery of the motion
of the chyle led to theories of digestion; the close
examination of the process of reproduction in plants and
animals led to theories of generation. In all these cases,
the discovery brought to light some portion of the process
which was mechanical or chemical, but it also, in each
instance, served to show that the process was something more
than mechanical or chemical. The theory attempted to explain
the process by the application of known causes; but there
always remained some part of it which must unavoidably be
referred to an unknown cause. But though unknown, such a
cause was not a hopeless object of study. As the vital
functions became better and better understood, it was seen
more and more clearly at what precise points of the process
it was necessary to assume a peculiar vital energy, and what
sort of properties {204} this energy must be conceived to
possess. It was perceived where, in what manner, in what
degree, mechanical and chemical agencies were modified,
over-ruled, or counteracted, by agencies which must be
hypermechanical and hyperchemical. And thus the discoveries
made in anatomy by a laborious examination of facts, pointed
out the necessity of introducing new ideas, in order that
the facts might be intelligible. Observation taught much;
and among other things, she taught that there was something
which could not be observed, but which must, if possible, be
conceived. I shall notice a few instances of this.
[Note 72\9: _Hist. Ind. Sc._ b. xvii.]
SECT. II.--_Attempts to form a distinct Conception of
Assimilation and Secretion._
2. _The Ancients._--That plants and animals grow by taking
into their substance matter previously extraneous, is
obvious to all: but as soon as we attempt to conceive this
process distinctly in detail, we find that it involves no
inconsiderable mystery. How does the same food become blood
and flesh, bone and hair? Perhaps the earliest attempt to
explain this mystery, is that recorded by Lucretius[73\9] as
the opinion of Anaxagoras, that food contains some bony,
some fleshy particles, some of blood, and so on. We might,
on this supposition, conceive that the mechanism of the body
appropriates each kind of particle to its suitable place.
[Note 73\9: Lucr. i. 855. Nunc et Anaxagoræ scrutemur
ὁμοιομέρειαν.]
But it is easy to refute this essay at philosophizing (as
Lucretius refutes it) by remarking that we do not find milk
in grass, or blood in fruit, though such food gives such
products in cattle and in men. In opposition to this
'Homoiomereia,' the opinion that is forced upon us by the
facts is, that the process of nutrition is not a selection
merely, but an _assimilation_; the organized system does not
_find_, but _make_, the additions to its structure. {205}
3. _Buffon._--This notion of _assimilation_ may be variously
expressed and illustrated; and all that we can do here, in
order to show the progress of thought, is to adduce the
speculations of those writers who have been most successful
in seizing and marking its peculiar character. Buffon may be
taken as an example of the philosophy of his time on this
subject. 'The body of the animal,' says he[74\9], 'is a kind
of _interior mould_, in which the matter subservient to its
increase is modelled and assimilated to the whole, in such a
way that, without occasioning any change in the order and
proportion of the parts, there results an augmentation in
each part taken separately. This increase, this development,
if we would have a _clear idea_ of it, how can we obtain it,
except by considering the body of the animal, and each of
the parts which is to be developed, as so many interior
moulds which only receive the accessory matter in the order
which results from the position of all their parts? This
development cannot take place, as persons sometimes persuade
themselves, by an addition to the outside; on the contrary,
it goes on by an intimate susception which penetrates the
mass; for, in the part thus developed, the size increases in
all parts proportionally, so that the new matter must
penetrate it in all its dimensions: and it is quite
necessary that this penetration of substance must take place
in a certain order, and according to a certain measure; for
if this were not so, some parts would develope themselves
more than others. Now what can there be which shall
prescribe such a rule to the accessory matter except the
_interior mould_?'
[Note 74\9: _Hist. Nat._ b. i. c. iii.]
To speak of a _mould_ simply, would convey a coarse
mechanical notion, which could not be received as any useful
contribution to physiological speculation. But this
_interior_ mould is, of course, to be understood
figuratively, not as an assemblage of cavities, but as a
collection of laws, shaping, directing, and modifying the
new matter; giving it not only form, but motion {206} and
activity, such as belong to the parts of an organic being.
4. It must be allowed, however, that even with this
explanation, the comparison is very loose and insufficient.
A _mould_ may be permitted to mean a collection of laws, but
still it can convey no conception except that of laws
regulated by relations of space; and such a conception is
very plainly quite inadequate to the purpose. What can we
conceive of the interior mould by which chyle is separated
from the aliments at the pores of the lacteals, or tears
secreted in the lacrymatory gland?
An additional objection to this mode of expression of Buffon
is, that it suggests to us only a single marked change in
the assimilated matter, not a continuous series of changes.
Yet the animal fluids and other substances are, in fact,
undergoing a constant series of changes. Food becomes chyme,
and chyme becomes chyle; chyle is poured into the blood;
from the blood secretions take place, as the bile; the bile
is poured into the digestive canal, and a portion of the
matter previously introduced is rejected out of the system.
Here we must have a series of 'interior moulds;' and these
must impress matter at its ejection from the organic system
as well as at its reception. But, moreover, it is probable
that none of the above transformations are quite abrupt.
Change is going on between the beginning and the end of each
stage of the nutritive circulation. To express the laws of
this continuous change, the image of an interior mould is
quite unsuited. We must seek a better mode of conception.
5. Vegetable and animal nutrition is, as we have said, a
constant circulation. The matter so assumed is not all
retained: a perpetual subtraction accompanies a perpetual
addition. There is an excretion as well as an
intussusception. The matter which is assumed by the living
creature is retained only for a while, and is then parted
with. The individual is the same, but its parts are in a
perpetual flux: they come and go. For a time the matter
which belongs to the organic body is bound to it by certain
laws: but before it is thus bound, and {207} after it is
loose, this matter may circulate about the universe in any
other form. Life consists in a permanent influence over a
perpetually changing set of particles.
_Cuvier._--This condition also has been happily expressed,
by means of a comparison, by another great naturalist. 'If,'
says Cuvier[75\9], 'if, in order to obtain a just idea of
the essence of life, we consider it in the beings where its
effects are most simple, we shall soon perceive that it
consists in the faculty which belongs to certain bodily
combinations to continue during a determinate time under a
determinate form; constantly attracting into their
composition a part of the surrounding substances, and giving
up in return some part of their own substance.
[Note 75\9: _Règne Animal_, i. 11.]
'Life is thus a _vortex_, more or less rapid, more or less
complex, which has a constant direction, and which always
carries along its stream particles of the same kinds; but in
which the individual particles are constantly entering in
and departing out; so that the _form_ of the living body is
more essential to it than its matter.
'So long as this motion subsists, the body in which it takes
place is _alive_; it _lives_. When the motion stops finally,
the body _dies_. After death, the elements which compose the
body, given up to the ordinary chemical affinities, soon
separate, and the body which was alive is dissolved.'
This notion of a vortex[76\9] which is permanent while the
matter which composes it constantly changes,--of peculiar
forces which act in this vortex so long as it exists, and
which give place to chemical forces when {208} the
circulatory motion ceases,--appears to express some of the
leading conditions of the assimilative power of living
things in a simple and general manner, and thus tends to
give distinctness to the notion of this vital function.
[Note 76\9: The definition of life given by M. de Blainville
appears to me not to differ essentially from that of Cuvier:
'Un corps vivant est une sorte de foyer chimique où il-y-a à
tous momens apport de nouvelles molecules et départ de
molecules anciennes; où la composition n'est jamais fixe (si
ce n'est d'un certain nombre de parties veritablement mortes
ou en depôt), mais toujours pour ainsi dire _in nisu_, d'où
mouvement plus ou moins lent et quelquefois
chaleur.'--_Principes d'Anat._ 1822, t. i. p. 16.]
6. But we may observe that this notion of a Vortex is still
insufficient. Particles are not only taken into the system
and circulated through it for a time, but, as we have seen,
they are altered in character in a manner to us
unintelligible, both at their first admission into the
system and at every period of their progress through it. In
the vortex each particle is constantly _transformed_ while
it whirls.
It may be said, perhaps, that this transformation of the
kinds of matter may be conceived to be merely a new
arrangement of their particles, and that thus all the
changes which take place in the circulating substances are
merely so many additional windings in the course of the
whirling current. But to say this, is to take for granted
the atomic hypothesis in its rudest form. What right have we
to assume that blood and tears, bile and milk, consist of
like particles of matter differently arranged? What can
arrangement, a mere relation of space, do towards explaining
such differences? Is not the insufficiency, the absurdity of
such an assumption proved by the whole course of science?
Are not even chemical changes, according to the best views
hitherto obtained, something more than a mere new
arrangement of particles? And are not vital as much beyond
chemical, as chemical are beyond geometrical modifications?
It is not enough, then, to conceive life as a vortex. The
particles which are taken into the organic frame do more
than circulate there. They are, at every point of their
circulation, acted upon by laws of an unknown kind, changing
the nature of the substance which they compose. Life is a
vortex in which vital forces act at every point of the
stream: it is not only a current of whirling _matter_, but a
cycle of recurring _powers_.
7. _Matter and Form._--This image of a vortex is closely
connected with the representation of life offered {209} us
by writers of a very different school. In Schelling's
_Lectures on Academic Study_, he takes a survey of the
various branches of human knowledge, determining according
to his own principles the shape which each science must
necessarily assume. The peculiar character of organization,
according to him[77\9], is that the matter is only an
accident of the thing itself, and the organization consists
in Form alone. But this Form, by its very opposition to
Matter, ceases to be independent of it, and is only ideally
separable. In organization, therefore, substance and
accident, matter and form, are completely identical[78\9].
This notion, that in organization the Form is essential and
the Matter accidental, or, in other words, that the Form is
permanent and the Matter fluctuating and transitory, agrees,
if taken in the grossest sense of matter and form, with
Cuvier's image of a Vortex. In a whirlpool, or in a
waterfall, the form remains, the matter constantly passes
away and is renewed. But we have already seen[79\9] that in
metaphysical speculations in which matter and form are
opposed, the word form is used in a far more extensive sense
than that which denotes a relation of space. It may indeed
designate any change which matter can undergo; and we may
very allowably say that food and blood are the same matter
under different _forms_. Hence if we assert that _Life is a
constant Form of a circulating Matter_, we express Cuvier's
notion in a mode free from the false suggestion which
'Vortex' conveys.
[Note 77\9: Lect. xiii. p. 288.]
[Note 78\9: I have not translated Schelling's words, but
given their import as far as I could.]
[Note 79\9: Book i.]
8. We may, however, still add something to this account of
life. The circulating parts of the system not only
circulate, but they form the non-circulating parts. Or
rather, there are no non-circulating parts: all portions of
the frame circulate more or less rapidly. The food which we
take circulates rapidly in the fluids, more slowly in the
flesh, still more slowly in the bones; but in all these
parts it is taken into the system, {210} retained there for
some time, and finally replaced by other matter. But while
it remains in the body, it exercises upon the other
circulating parts the powers by which their motion is
produced. Nutriment forms and supports the organs, and the
organs carry fresh nutriment to its destination. The
peculiar forces of the living body, and its peculiar
structure, are thus connected in an indescribable manner.
The forces produce the structure; the structure, again, is
requisite for the exertion of the forces. The Idea of an
Organic or Living Being includes this peculiar
condition--that its construction and powers are such, that
it constantly appropriates to itself new portions of
substance which, so appropriated, become indistinguishable
parts of the whole, and serve to carry on subsequently the
same functions by which they were assimilated. And thus
_Organic Life is a constant Form of a circulating Matter, in
which the Matter and the Form determine each other by
peculiar laws_ (_that is, by Vital Forces_).
SECT. III.--_Attempts to conceive the forces of Assimilation
and Secretion._
9. I have already stated that in our attempts to obtain
clear and scientific Ideas of Vital Forces, we have, in the
first place, to seek to understand the course of change and
motion in each function, so as to see at what points of the
process peculiar causes come into play; and next, to
endeavour to obtain some insight into the peculiar character
and attributes of these causes. Having spoken of the first
part of this mode of investigation in regard to the general
nutrition of organic bodies, I must now say a few words on
the second part.
The Forces here spoken of are _Vital_ Forces. From what has
been said, we may see in some measure the distinction
between forces of this kind and mechanical or chemical
forces; the latter tend constantly to produce a final
condition, after which there is no further cause of change:
mechanical forces tend to produce equilibrium; chemical
forces tend to produce {211} composition or decomposition;
and this point once reached, the matter in which these
forces reside is altogether inert. But an organic body tends
to a constant motion, and the highest activity of organic
forces shows itself in continuous change. Again, in
mechanical and chemical forces, the force of any aggregate
is the sum of the forces of all the parts: the sum of the
forces corresponds to the sum of the matter. But in organic
bodies, the amount of effect does not depend on the matter,
but on the form: the particles lose their separate energy,
in order to share in that of the system; they are not added,
they are _assimilated_.
10. It is difficult to say whether anything has been gained
to science by the various attempts to assign a fixed _name_
to the vital force which is thus the immediate cause of
Assimilation. It has been called _Organic Attraction_ or
_Vital Attraction_, _Organic Affinity_ or _Vital Affinity_,
being thus compared with mechanical Attraction or chemical
Affinity. But, perhaps, as the process is certainly neither
mechanical nor chemical, it is desirable to appropriate to
it a peculiar name; and the name _Assimilation_, or _Organic
Assimilation_, by the usage of good biological writers, is
generally employed for this purpose, and may be taken as the
standard name of this Vital Force. To illustrate this, I
will quote a passage from the excellent _Elements of
Physiology_ of Professor Müller. 'In the process of
nutrition is exemplified the fundamental principle of
_organic assimilation_. Each elementary particle of an organ
attracts similar particles from the blood, and by the
changes it produces in them, causes them to participate in
the vital principle of the organ itself. Nerves take up
nervous substance, muscles, muscular substance: even morbid
structures have the assimilating power; warts in the skin
grow with their own peculiar structure; in an ulcer, the
base and border are nourished in a way conformable to the
mode of action and secretion determined by the disease.'
11. The Force of Organic Assimilation spoken of in the last
paragraph denotes peculiarly the force by which each organ
appropriates to itself a part of the {212} nutriment
received into the system, and thus is maintained and
augmented with the growth of the whole. But the growth of
the solid parts is only one portion of the function of
nutrition; besides this, we must consider the motion and
changes of the fluids, and must ask what kind of forces may
be conceived to produce these. What are the powers by which
chyle is _absorbed_ from the food, by which bile is
_secreted_ from the blood, by which the circulating _motion_
of these and all other fluids of the body are constantly
maintained? To the questions,--What are the forces by which
_absorption_, _secretion_, and the _vital motions_, of
fluids are produced?--no satisfactory answer has been
returned. Yet still some steps have been made, which it may
be instructive to point out.
12. In _Absorption_ it would appear that a part of the
agency is inorganic; for not only dead membranes, but
inorganic substances, absorb fluids, and even absorb them
with elective forces, according to the ingredients, of the
fluid. A force which is of this kind, and which has been
termed _Endosmose_, has been found to produce very curious
effects. When a membrane separates two fluids, holding in
solution different ingredients, the fluids pass through the
membrane in an imperceptible manner, and mix or exchange
their elements. The force which produces these effects is
capable of balancing a very considerable pressure. It
appears, moreover, to depend, at least among other causes,
upon attractions operating between the elements of the
solids and the fluids, as well as between the different
fluids; and this force, though thus apparently of a
mechanical and chemical nature, probably has considerable
influence in vital phenomena.