origin, was merely natural history; it registered the phenomena of
disease, classified them, and ventured upon a prognosis, wherever the
observation of constant co-existences and sequences suggested a
rational expectation of the like recurrence under similar
circumstances.
Further than this it hardly went. In fact, in the then state of
knowledge, and in the condition of philosophical speculation at that
time, neither the causes of the morbid state, nor the _rationale_
of treatment, were likely to be sought for as we seek for them now. The
anger of a god was a sufficient reason for the existence of a malady,
and a dream ample warranty for therapeutic measures; that a physical
phenomenon must needs have a physical cause was not the implied or
expressed axiom that it is to us moderns.
The great man whose name is inseparably connected with the foundation
of medicine, Hippocrates, certainly knew very little, indeed
practically nothing, of anatomy or physiology; and he would, probably,
have been perplexed even to imagine the possibility of a connection
between the zoological studies of his contemporary Democritus and
medicine. Nevertheless, in so far as he, and those who worked before
and after him, in the same spirit, ascertained, as matters of
experience, that a wound, or a luxation, or a fever, presented such and
such symptoms, and that the return of the patient to health was
facilitated by such and such measures, they established laws of nature,
and began the construction of the science of pathology. All true
science begins with empiricism--though all true science is such
exactly, in so far as it strives to pass out of the empirical stage
into that of the deduction of empirical from more general truths. Thus,
it is not wonderful, that the early physicians had little or nothing to
do with the development of biological science; and, on the other hand,
that the early biologists did not much concern themselves with
medicine. There is nothing to show that the Asclepiads took any
prominent share in the work of founding anatomy, physiology, zoology,
and botany. Rather do these seem to have sprung from the early
philosophers, who were essentially natural philosophers, animated by
the characteristically Greek thirst for knowledge as such. Pythagoras,
Alcmeon, Democritus, Diogenes of Apollonia, are all credited with
anatomical and physiological investigations; and, though Aristotle is
said to have belonged to an Asclepiad family, and not improbably owed
his taste for anatomical and zoological inquiries to the teachings of
his father, the physician Nicomachus, the "Historia Animalium," and the
treatise "De Partibus Animalium," are as free from any allusion to
medicine as if they had issued from a modern biological laboratory.
It may be added, that it is not easy to see in what way it could have
benefited a physician of Alexander's time to know all that Aristotle
knew on these subjects. His human anatomy was too rough to avail much
in diagnosis; his physiology was too erroneous to supply data for
pathological reasoning. But when the Alexandrian school, with
Erasistratus and Herophilus at their head, turned to account the
opportunities of studying human structure, afforded to them by the
Ptolemies, the value of the large amount of accurate knowledge thus
obtained to the surgeon for his operations, and to the physician for
his diagnosis of internal disorders, became obvious, and a connection
was established between anatomy and medicine, which has ever become
closer and closer. Since the revival of learning, surgery, medical
diagnosis, and anatomy have gone hand in hand. Morgagni called his
great work, "De sedibus et causis morborum per anatomen indagatis," and
not only showed the way to search out the localities and the causes of
disease by anatomy, but himself travelled wonderfully far upon the
road. Bichat, discriminating the grosser constituents of the organs and
parts of the body, one from another, pointed out the direction which
modern research must take; until, at length, histology, a science of
yesterday, as it seems to many of us, has carried the work of Morgagni
as far as the microscope can take us, and has extended the realm of
pathological anatomy to the limits of the invisible world.
Thanks to the intimate alliance of morphology with medicine, the
natural history of disease has, at the present day, attained a high
degree of perfection. Accurate regional anatomy has rendered
practicable the exploration of the most hidden parts of the organism,
and the determination, during life, of morbid changes in them;
anatomical and histological post-mortem investigations have supplied
physicians with a clear basis upon which to rest the classification, of
diseases, and with unerring tests of the accuracy or inaccuracy of
their diagnoses.
If men could be satisfied with pure knowledge, the extreme precision
with which, in these days, a sufferer may be told what is happening,
and what is likely to happen, even in the most recondite parts of his
bodily frame, should be as satisfactory to the patient as it is to
the scientific pathologist who gives him the information. But I am
afraid it is not; and even the practising physician, while nowise
under-estimating the regulative value of accurate diagnosis, must often
lament that so much of his knowledge rather prevents him from doing
wrong than helps him to do right.
A scorner of physic once said that nature and disease may be compared
to two men fighting, the doctor to a blind man with a club, who strikes
into the _mêlée_, sometimes hitting the disease, and sometimes
hitting nature. The matter is not mended if you suppose the blind man's
hearing to be so acute that he can register every stage of the
struggle, and pretty clearly predict how it will end. He had better not
meddle at all, until his eyes are opened, until he can see the exact
position of the antagonists, and make sure of the effect of his blows.
But that which it behoves the physician to see, not, indeed, with his
bodily eye, but with clear, intellectual vision, is a process, and the
chain of causation involved in that process. Disease, as we have seen,
is a perturbation of the normal activities of a living body, and it is,
and must remain, unintelligible, so long as we are ignorant of the
nature of these normal activities. In other words, there could be no
real science of pathology until the science of physiology had reached a
degree of perfection unattained, and indeed unattainable, until quite
recent times.
So far as medicine is concerned, I am not sure that physiology, such as
it was down to the time of Harvey, might as well not have existed. Nay,
it is perhaps no exaggeration to say that, within the memory of living
men, justly renowned practitioners of medicine and surgery knew
less physiology than is now to be learned from the most elementary
text-book; and, beyond a few broad facts, regarded what they did know
as of extremely little practical importance. Nor am I disposed to blame
them for this conclusion; physiology must be useless, or worse than
useless, to pathology, so long as its fundamental conceptions are
erroneous.
Harvey is often said to be the founder of modern physiology; and there
can be no question that the elucidations of the function of the heart,
of the nature of the pulse, and of the course of the blood, put forth
in the ever-memorable little essay, "De motu cordis," directly worked a
revolution in men's views of the nature and of the concatenation of
some of the most important physiological processes among the higher
animals; while, indirectly, their influence was perhaps even more
remarkable.
But, though Harvey made this signal and perennially important
contribution to the physiology of the moderns, his general conception
of vital processes was essentially identical with that of the ancients;
and, in the "Exercitationes de generatione," and notably in the
singular chapter "De calido innato," he shows himself a true son of
Galen and of Aristotle.
For Harvey, the blood possesses powers superior to those of the
elements; it is the seat of a soul which is not only vegetative, but
also sensitive and motor. The blood maintains and fashions all parts of
the body, "idque summâ cum providentiâ et intellectu in finem certum
agens, quasi ratiocinio quodam uteretur."
Here is the doctrine of the "pneuma," the product of the philosophical
mould into which the animism of primitive men ran in Greece, in full
force. Nor did its strength abate for long after Harvey's time. The
same ingrained tendency of the human mind to suppose that a process is
explained when it is ascribed to a power of which nothing is known
except that it is the hypothetical agent of the process, gave rise, in
the next century, to the animism of Stahl; and, later, to the doctrine
of a vital principle, that "asylum ignorantiae" of physiologists, which
has so easily accounted for everything and explained nothing, down to
our own times.
Now the essence of modern, as contrasted with ancient, physiological
science appears to me to lie in its antagonism to animistic hypotheses
and animistic phraseology. It offers physical explanations of vital
phenomena, or frankly confesses that it has none to offer. And, so far
as I know, the first person who gave expression to this modern view of
physiology, who was bold enough to enunciate the proposition that vital
phenomena, like all the other phenomena of the physical world, are, in
ultimate analysis, resolvable into matter and motion, was René
Descartes.
The fifty-four years of life of this most original and powerful thinker
are widely overlapped, on both sides, by the eighty of Harvey, who
survived his younger contemporary by seven years, and takes pleasure in
acknowledging the French philosopher's appreciation of his great
discovery.
In fact, Descartes accepted the doctrine of the circulation as
propounded by "Harvaeus médecin d'Angleterre," and gave a full account
of it in his first work, the famous "Discours de la Méthode," which was
published in 1637, only nine years after the exercitation "De motu
cordis"; and, though differing from Harvey on some important points (in
which it may be noted, in passing, Descartes was wrong and Harvey
right), he always speaks of him with great respect. And so important
does the subject seem to Descartes, that he returns to it in the
"Traité des Passions," and in the "Traité de l'Homme."
It is easy to see that Harvey's work must have had a peculiar
significance for the subtle thinker, to whom we owe both the
spiritualistic and the materialistic philosophies of modern times. It
was in the very year of its publication, 1628, that Descartes withdrew
into that life of solitary investigation and meditation of which his
philosophy was the fruit. And, as the course of his speculations led
him to establish an absolute distinction of nature between the material
and the mental worlds, he was logically compelled to seek for the
explanation of the phenomena of the material world within itself; and
having allotted the realm of thought to the soul, to see nothing but
extension and motion in the rest of nature. Descartes uses "thought" as
the equivalent of our modern term "consciousness." Thought is the
function of the soul, and its only function. Our natural heat and all
the movements of the body, says he, do not depend on the soul. Death
does not take place from any fault of the soul, but only because some
of the principal parts of the body become corrupted. The body of a
living man differs from that of a dead man in the same way as a watch
or other automaton (that is to say, a machine which moves of itself)
when it is wound up and has, in itself, the physical principle of the
movements which the mechanism is adapted to perform, differs from the
same watch, or other machine, when it is broken, and the physical
principle of its movement no longer exists. All the actions which are
common to us and the lower animals depend only on the conformation of
our organs, and the course which the animal spirits take in the brain,
the nerves, and the muscles; in the same way as the movement of a watch
is produced by nothing but the force of its spring and the figure of
its wheels and other parts.
Descartes' "Treatise on Man" is a sketch of human physiology, in which
a bold attempt is made to explain all the phenomena of life, except
those of consciousness, by physical reasonings. To a mind turned in
this direction, Harvey's exposition of the heart and vessels as a
hydraulic mechanism must have been supremely welcome.
Descartes was not a mere philosophical theorist, but a hardworking
dissector and experimenter, and he held the strongest opinion
respecting the practical value of the new conception which he was
introducing. He speaks of the importance of preserving health, and of
the dependence of the mind on the body being so close that, perhaps,
the only way of making men wiser and better than they are, is to be
sought in medical science. "It is true," says he, "that as medicine is
now practised it contains little that is very useful; but without any
desire to depreciate, I am sure that there is no one, even among
professional men, who will not declare that all we know is very little
as compared with that which remains to be known; and that we might
escape an infinity of diseases of the mind, no less than of the body,
and even perhaps from the weakness of old age, if we had sufficient
knowledge of their causes, and of all the remedies with which nature
has provided us." [1] So strongly impressed was Descartes with this,
that he resolved to spend the rest of his life in trying to acquire
such a knowledge of nature as would lead to the construction of a
better medical doctrine. [2] The anti-Cartesians found material for
cheap ridicule in these aspirations of the philosopher; and it is
almost needless to say that, in the thirteen years which elapsed
between the publication of the "Discours" and the death of Descartes,
he did not contribute much to their realisation. But, for the next
century, all progress in physiology took place along the lines which
Descartes laid down.
The greatest physiological and pathological work of the seventeenth
century, Borelli's treatise "De Motu Animalium," is, to all intents and
purposes, a development of Descartes' fundamental conception; and the
same may be said of the physiology and pathology of Boerhaave, whose
authority dominated in the medical world of the first half of the
eighteenth century.
With the origin of modern chemistry, and of electrical science, in the
latter half of the eighteenth century, aids in the analysis of the
phenomena of life, of which Descartes could not have dreamed, were
offered to the physiologist. And the greater part of the gigantic
progress which has been made in the present century is a justification
of the prevision of Descartes. For it consists, essentially, in a more
and more complete resolution of the grosser organs of the living body
into physicochemical mechanisms.
"I shall try to explain our whole bodily machinery in such a way, that
it will be no more necessary for us to suppose that the soul produces
such movements as are not voluntary, than it is to think that there is
in a clock a soul which causes it to show the hours." [3] These words
of Descartes might be appropriately taken as a motto by the author of
any modern treatise on physiology.
But though, as I think, there is no doubt that Descartes was the first
to propound the fundamental conception of the living body as a physical
mechanism, which is the distinctive feature of modern, as contrasted
with ancient physiology, he was misled by the natural temptation to
carry out, in all its details, a parallel between the machines with
which he was familiar, such as clocks and pieces of hydraulic
apparatus, and the living machine. In all such machines there is a
central source of power, and the parts of the machine are merely
passive distributors of that power. The Cartesian school conceived of
the living body as a machine of this kind; and herein they might have
learned from Galen, who, whatever ill use he may have made of the
doctrine of "natural faculties," nevertheless had the great merit of
perceiving that local forces play a great part in physiology.
The same truth was recognised by Glisson, but it was first prominently
brought forward in the Hallerian doctrine of the "vis insita" of
muscles. If muscle can contract without nerve, there is an end of the
Cartesian mechanical explanation of its contraction by the influx of
animal spirits.
The discoveries of Trembley tended in the same direction. In the
freshwater _Hydra_, no trace was to be found of that complicated
machinery upon which the performance of the functions in the higher
animals was supposed to depend. And yet the hydra moved, fed, grew,
multiplied, and its fragments exhibited all the powers of the whole.
And, finally, the work of Caspar F. Wolff, [4] by demonstrating the
fact that the growth and development of both plants and animals take
place antecedently to the existence of their grosser organs, and are,
in fact, the causes and not the consequences of organisation (as then
understood), sapped the foundations of the Cartesian physiology as a
complete expression of vital phenomena.
For Wolff, the physical basis of life is a fluid, possessed of a "vis
essentialis" and a "solidescibilitas," in virtue of which it gives rise
to organisation; and, as he points out, this conclusion strikes at the
root of the whole iatro-mechanical system.
In this country, the great authority of John Hunter exerted a similar
influence; though it must be admitted that the too sibylline utterances
which are the outcome of Hunter's struggles to define his conceptions
are often susceptible of more than one interpretation. Nevertheless, on
some points Hunter is clear enough. For example, he is of opinion that
"Spirit is only a property of matter" ("Introduction to Natural
History," p. 6), he is prepared to renounce animism, (_l.c._ p.
8), and his conception of life is so completely physical that he thinks
of it as something which can exist in a state of combination in the
food. "The aliment we take in has in it, in a fixed state, the real
life; and this does not become active until it has got into the lungs;
for there it is freed from its prison" ("Observations on Physiology,"
p. 113). He also thinks that "It is more in accord with the general
principles of the animal machine to suppose that none of its effects
are produced from any mechanical principle whatever; and that every
effect is produced from an action in the part; which action is produced
by a stimulus upon the part which acts, or upon some other part with
which this part sympathises so as to take up the whole action" (_l.c._
p. 152).
And Hunter is as clear as Wolff, with whose work he was probably
unacquainted, that "whatever life is, it most certainly does not depend
upon structure or organisation" (_l.c._ p. 114).
Of course it is impossible that Hunter could have intended to deny the
existence of purely mechanical operations in the animal body. But
while, with Borelli and Boerhaave, he looked upon absorption,
nutrition, and secretion as operations effected by means of the small
vessels, he differed from the mechanical physiologists, who regarded
these operations as the result of the mechanical properties of the
small vessels, such as the size, form, and disposition of their canals
and apertures. Hunter, on the contrary, considers them to be the effect
of properties of these vessels which are not mechanical but vital. "The
vessels," says he, "have more of the polypus in them than any other
part of the body," and he talks of the "living and sensitive principles
of the arteries," and even of the "dispositions or feelings of the
arteries." "When the blood is good and genuine the sensations of the
arteries, or the dispositions for sensation, are agreeable.... It is
then they dispose of the blood to the best advantage, increasing the
growth of the whole, supplying any losses, keeping up a due succession,
etc." (_l.c._ p. 133).
If we follow Hunter's conceptions to their logical issue, the life of
one of the higher animals is essentially the sum of the lives of all
the vessels, each of which is a sort of physiological unit, answering
to a polype; and, as health is the result of the normal "action of the
vessels," so is disease an effect of their abnormal action. Hunter thus
stands in thought, as in time, midway between Borelli on the one hand,
and Bichat on the other.
The acute founder of general anatomy, in fact, outdoes Hunter in his
desire to exclude physical reasonings from the realm of life. Except in
the interpretation of the action of the sense organs, he will not allow
physics to have anything to do with physiology.
"To apply the physical sciences to physiology is to explain the
phenomena of living bodies by the laws of inert bodies. Now this is a
false principle, hence all its consequences are marked with the same
stamp. Let us leave to chemistry its affinity; to physics, its
elasticity and its gravity. Let us invoke for physiology only
sensibility and contractility." [5]
Of all the unfortunate dicta of men of eminent ability this seems one
of the most unhappy, when we think of what the application of the
methods and the data of physics and chemistry has done towards bringing
physiology into its present state. It is not too much to say that
one-half of a modern text-book of physiology consists of applied
physics and chemistry; and that it is exactly in the exploration of the
phenomena of sensibility and contractility that physics and chemistry
have exerted the most potent influence.
Nevertheless, Bichat rendered a solid service to physiological progress
by insisting upon the fact that what we call life, in one of the higher
animals, is not an indivisible unitary archaeus dominating, from its
central seat, the parts of the organism, but a compound result of the
synthesis of the separate lives of those parts.
"All animals," says he, "are assemblages of different organs, each of
which performs its function and concurs, after its fashion, in the
preservation of the whole. They are so many special machines in the
general machine which constitutes the individual. But each of these
special machines is itself compounded of many tissues of very different
natures, which in truth constitute the elements of those organs"
(_l.c._ lxxix.). "The conception of a proper vitality is applicable
only to these simple tissues, and not to the organs themselves"
(_l.c._ lxxxiv.).
And Bichat proceeds to make the obvious application of this doctrine of
synthetic life, if I may so call it, to pathology. Since diseases are
only alterations of vital properties, and the properties of each tissue
are distinct from those of the rest, it is evident that the diseases of
each tissue must be different from those of the rest. Therefore, in any
organ composed of different tissues, one may be diseased and the other
remain healthy; and this is what happens in most cases (_l.c._ lxxxv.).
In a spirit of true prophecy, Bichat says, "We have arrived at an epoch
in which pathological anatomy should start afresh." For, as the
analysis of the organs had led him to the tissues as the physiological
units of the organism; so, in a succeeding generation, the analysis of
the tissues led to the cell as the physiological element of the
tissues. The contemporaneous study of development brought out the same
result; and the zoologists and botanists, exploring the simplest and
the lowest forms of animated beings, confirmed the great induction of
the cell theory. Thus the apparently opposed views, which have been
battling with one another ever since the middle of the last century,
have proved to be each half the truth.