Chapter V (7)

[818] I formerly adopted the commonly received division of organic
statics, and organic dynamics; the statics being anatomy, and the
dynamics being physiology. But, I now think that our knowledge is
not sufficiently advanced to make this so convenient as the
division into physiological and pathological, or into normal and
abnormal, provided we remember that in reality nothing is
abnormal. The practically useful, but eminently unscientific,
doctrine, that there can be alteration of function without
alteration of structure, has effaced some of the most essential
distinctions between anatomy and physiology, and especially
between morbid anatomy and morbid physiology. Until those
distinctions are recognized, the scientific conceptions of
professional writers must be confused, however valuable their
practical suggestions may be. While men are capable of believing
that it is _possible_ for variations of function to proceed from
any cause except variations of structure, the philosophic
importance of anatomy will be imperfectly appreciated, and its
true relation to physiology will remain undefined. Inasmuch,
however, as, with our actual resources, the most careful
dissection is often unable to detect (in insanity, for instance)
those changes of structure which produce changes of function,
superficial thinkers are placed under a strong temptation to deny
their invariable connexion; and while the microscope is so
imperfect, and chemistry so backward, it is impossible that
experiments should always convince them of their mistake. Hence, I
believe that until our means of empirical research are greatly
improved, all such investigations, notwithstanding their immense
value in other respects, will tend to lead mere inductive minds
into error, by making them rely too much on what they call the
facts of the case, to the prejudice of the reason. This is what I
mean by saying, that our knowledge is not sufficiently advanced to
make it advisable to divide the sciences of organic bodies into
physiological and anatomical. At present, and probably for some
time yet, the humbler division into physiological and
pathological, may be deemed safer, and more likely to produce
solid results.

The science of pathology being still so backward in the conception as well as in the execution, that even men of real ability believe that it can be raised from a mere study of the human frame, it will hardly be expected that the Scotch, notwithstanding the marvellous boldness of their speculations, should have been able, in the eighteenth century, to anticipate a method which the nineteenth century has yet to employ. But they produced two pathologists of great ability, and to whom we owe considerable obligations. These were, Cullen and John Hunter.[819] Cullen was eminent only as a pathologist; but Hunter, whose fine and discursive genius took a much wider range, was great both in physiology and in pathology. A short account of their generalizations respecting organic science, will be a fitting sequel to the notices I have already given of what was done by their countrymen for inorganic science, during the same period. It will complete our survey of the Scotch intellect, and will enable the reader to form some idea of the brilliant achievements of that most remarkable people, who, contrary to the course of affairs in all other modern nations, have shown that scientific discoveries do not necessarily weaken superstition, and that it is possible for two hostile principles to flourish side by side, without ever coming into actual collision, or without sensibly impairing each other's vigour.

[819] Hunter, as we shall presently see, did take an extraordinarily
comprehensive view of pathology, including the whole of the
organic world and even the aberrations of form in the inorganic.

In 1751, Cullen was appointed professor of medicine in the University of Glasgow;[820] from which, however, in 1756, he was removed to the University of Edinburgh,[821] where he delivered those celebrated lectures, on which his fame now depends. During the early part of his career, he paid great attention to inorganic physics, and propounded some remarkable speculations, which are supposed to have suggested the theory of latent heat to Black, who was his pupil.[822] But, to follow out those views, would have required a number of minute experiments, which it did not suit the habit of his mind to make. Having, therefore, put forth his ideas, he left them to germinate, and passed on to his arduous attempt to generalize the laws of disease as they are exhibited in the human frame. In the study of disease, the phenomena being more obscure and less amenable to experiment, there was greater latitude for speculation; hence, he could more easily indulge in that love of theory, which was his ruling passion, and with an extreme devotion to which he has been reproached.[823] That the reproach is not altogether unjust, must, I think, be admitted, since we find him laying down the doctrine, that, inasmuch as, in the treatment of disease, theory could not be separated from practice, it was unimportant which came first.[824] This was tantamount to saying, that a medical practitioner might allow his theories to control his observations; for it is certain that, in an immense majority of cases, men are so tenacious of the opinions they imbibe, that whatever, in any pursuit, first occupies their understanding, is likely to mould all that comes afterwards. In ordinary minds, associations of ideas, if firmly established, become indissoluble; and the power of separating them, and of arranging them in new combinations, is one of the rarest of our endowments. An average intellect, when once possessed by a theory, can hardly ever escape from it. Hence, in practical matters, theory should be feared, just as, in scientific matters, it should be cherished; because practical pursuits are chiefly engrossed by the lower class of minds, where associations and the force of prejudice are extremely strong, while scientific pursuits concern the higher class, where such prepossessions are comparatively weak, and where close associations are more easily severed. The most powerful intellects are most accustomed to new arrangements of thought, and are, therefore, most able to break up old ones. On them, belief sits lightly, because they well know how little evidence we have for many of even our oldest beliefs. But the average, or, as we must say, without meaning offence, the inferior, minds, are not disturbed by these refinements. Theories, which they have once heartily embraced, they can hardly ever get rid of, and they often dignify them with the name of essential truths, and resent every attack upon them as a personal injury. Having inherited such theories from their fathers, they regard them with a sort of filial piety, and cling to them as if they were some rich acquisition, which no one has a right to touch.

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

[821] _Thomson's Life of Cullen_, vol. i. p. 96. Bower states that
Cullen 'was appointed to the chair in 1755.' _Bower's History of
the University of Edinburgh_, vol. ii. p. 216, Edinburgh, 1817.

[822] 'It seems impossible to peruse the passages I have quoted from
Dr. Cullen's manuscript lectures and papers, and from his Essay on
Evaporation, without perceiving that his investigations with
regard to the heat and cold occasioned by the combination,
liquefaction, and evaporation of bodies, must not only have
assisted to direct the attention of his pupil Dr. Black to similar
inquiries, but must also have furnished him with several of the
data from which his simple and comprehensive theory of Latent Heat
was afterwards so philosophically deduced.' _Thomson's Life of
Cullen_, vol. i. p. 56.

[823] 'It is allowed by the admirers of this great man, that he was
perhaps too fond of theory.' _Bower's History of the University of
Edinburgh_, vol. iii. p. 273

[824] In 1759, he wrote to Dr. Balfour Russell, one of his favourite
pupils: 'You will not find it possible to separate practice from
theory altogether; and therefore, if you have a mind to begin with
the theory, I have no objection.' _Thomson's Life of Cullen_, vol.
i. p. 130. Compare his _Introductory Lectures to the Practice of
Physic_, where, asserting truly, 'that reasoning in physic is
unavoidable' (_Cullen's Works_, vol. i. p. 417), he boldly infers,
'that to render it safe, it is _necessary to cultivate theory in
its full extent_.'

To this latter class, nearly all men belong, who are more engaged in practical pursuits than in speculative ones. Among them, are the ordinary practitioners, whether in medicine or in any other department, extremely few of whom are willing to break up trains of thought to which they are inured.[825] Though they profess to despise theory, they are, in reality, enslaved by it. All that they can do, is to conceal their subjection, by terming their theory a necessary belief. It must, therefore, be deemed a remarkable proof of Cullen's love of deductive reasoning, that he, sagacious and clear-sighted as he was, should have supposed that, in so practical an art as medicine, theory could, with impunity, precede practice. For, it is most assuredly true, that, taking men in the average, their minds are so constructed, that it cannot precede it without controlling it. It is equally true, that such control must be hurtful. Even now, and notwithstanding the great steps which have been taken in morbid anatomy, in animal chemistry, and in the microscopic investigation both of the fluids and solids of the human frame, the treatment of disease is a question of art, far more than a question of science. What chiefly characterizes the most eminent physicians, and gives them their real superiority, is not so much the extent of their theoretical knowledge,--though that, too, is often considerable,--but it is that fine and delicate perception which they owe, partly to experience, and partly to a natural quickness in detecting analogies and differences which escape ordinary observers. The process which they follow, is one of rapid, and, in some degree, unconscious, induction. And this is the reason why the greatest physiologists and chemists, which the medical profession possesses, are not, as a matter of course, the best curers of disease. If medicine were a science, they would always be the best. But medicine, being still essentially an art, depends mainly upon qualities which each practitioner has to acquire for himself, and which no scientific theory can teach. The time for a general theory has not yet come, and probably many generations will have to elapse before it does come. To suppose, therefore, that a theory of disease should, as a matter of education, precede the treatment of disease, is not only practically dangerous, but logically false. With its practical danger I am not now concerned; but its logical aspect is a curious illustration of that passion for systematic and dialectic reasoning which characterized Scotland. It shows that Cullen, in his eagerness to argue from principles to facts, instead of from facts to principles, could, in the most important of all arts, recommend a method of procedure, for which even our knowledge is not ripe, but which, in his time, was so singularly rash and immature, that nothing can explain its adoption by a man of such vigorous understanding, except the circumstance of his living in a country in which that peculiar method reigned supreme.

[825] Even Cullen himself says, rather roughly, 'The great horde of
physicians are always servile imitators, who can neither perceive
nor correct the faults of their system, and are always ready to
growl at, and even to worry, the ingenious person that could
attempt it. Thus was the system of Galen secured in the possession
of the schools of physic, till soon after the irruption of the
Goths and Vandals destroyed every vestige of literature in the
western parts of Europe, and drove all that remained of it to seek
a feeble protection at Constantinople.' _Lectures Introductory to
the Practice of Physic_, in _Cullen's Works_, vol. i. p. 386,
Edinburgh, 1827.

It must, however, be admitted that Cullen wielded the method with great ability, especially in his application of it to the science of pathology, to which it was far better suited than to the art of therapeutics. For, we must always remember, that the science which investigates the laws of disease, is quite a different thing from the art which cures it. The science has a speculative interest, which is irrespective of all practical considerations, and which depends simply on the fact, that, when it is completed, it will explain the aberrations of the whole organic world. Pathology aims at ascertaining the causes which determine every departure from the natural type, whether of form or of function. Hence it is, that no one can take a comprehensive view of the actual state of knowledge, without studying the theoretic relations between pathology and other departments of inquiry. To do this, is the business, not of practical men, but of philosophers, properly so called. The philosophic pathologist is as different from the physician, as a jurist is different from an advocate, or as an agricultural chemist is different from a farmer, or as a political economist is different from a statesman, or as an astronomer, who generalizes the laws of the heavenly bodies, is different from a captain, who navigates his ship by a practical application of those laws. The two sets of functions may be united, and occasionally, though very rarely, they are, but there is no necessity for their being so. While, therefore, it would be absurdly presumptuous for an unprofessional person to pass judgment on the therapeutical system of Cullen, it is perfectly legitimate for any one, who has studied the theory of these matters, to examine his pathological system; because that, like all scientific systems, must be amenable to general considerations, which are to be taken, partly from the adjoining sciences, and partly from the universal logic of philosophic method.

It is from this latter, or logical, point of view, that Cullen's pathology is interesting for the purposes of the present chapter. The character of his investigations may be illustrated by saying, that his method in pathology is analogous to that which Adam Smith adopted at the same time, though in a very different field. Both were deductive; and both, before arguing deductively, suppressed some of the premisses from which they reasoned. That this suppression is the key to Adam Smith's method, and was an intentional part of his plan, I have already shown; as also that, in each of his two works, he supplied the premisses in which the other work was deficient. In this respect, he was far superior to Cullen. For, though Cullen, like Smith, began by mutilating his problem in order to solve it more readily, he, unlike Smith, did not see the necessity of instituting another and parallel inquiry, which should complete the scheme, by starting from the premisses that had been previously omitted.

What I have termed the mutilation of the problem, was effected by Cullen in the following manner. His object was, to generalize the phenomena of disease, as they are exhibited in the human frame; and it was obvious to him, as to every one else, that the human frame consists partly of solids and partly of fluids. The peculiarity of his pathology is, that he reasons almost entirely from the laws of the solids, and makes so little account of the fluids, that he will only allow them to be the indirect causes of disease, which, in a scientific view, are to be deemed strictly subordinate to the direct causes, as represented by the solid constituents of our body.[826] This assumption, though false, was perfectly justifiable, since, by curtailing the problem, he simplified its study; just as Adam Smith, in his _Wealth of Nations_, simplified the study of human nature, by curtailing it of all its sympathy. But this most comprehensive thinker was careful, in his _Theory of Moral Sentiments_, to restore to human nature the quality of which the _Wealth of Nations_ had deprived it; and, by thus establishing two different lines of argument, he embraced the whole subject. In the same way, it was incumbent on Cullen, after having constructed a theory of disease by reasoning from the solids, to have constructed another theory by reasoning from the fluids; so that a coördination of the two theories might have raised a science of pathology, as complete as the then state of knowledge allowed.[827] But to this, his mind was unequal. Able though he was, he lacked the grasp of intellect which characterized Adam Smith, and which made that great man perceive, that every deductive argument which is founded on a suppression of premisses, must be compensated by a parallel argument, which takes those premisses into account.[828] So little was Cullen aware of this, that, having built up that system of pathology which is known to medical writers as Solidism, he never took the pains to accompany it by another system, which gave the first rank to the fluids. On the contrary, he believed that his plan was complete and exhaustive, and that what is termed Humoral Pathology was a fiction, which had too long usurped the place of truth.[829]

[826] This idea runs through the whole of his writings. In the following
passage, it is more succinctly stated than in any other: 'In
pathology, and in the prognosis of particular diseases, it is
absolutely necessary to enter into the distinction of these
causes. I call the one _direct_ causes, those which act upon the
nervous system directly; and the other _indirect_ causes, those
which produce the same effect, but by destroying those organs
which are necessary to the support of the excitement, viz. the
whole system of circulation.' _Cullen's Works_, vol. i. p. 135.
Even this passage, clear as it seems, can only be rightly
interpreted by taking the context into consideration.

[827] For, as is truly observed by probably the greatest pathologist of
our time, 'Humoral pathology is simply a requirement of common
practical sense; and it has always held a place in medical
science, although the limits of its domain have, no doubt, been
variously circumscribed or interpreted at different times. Of late
years, it has met with a new basis and support in morbid anatomy,
which, in the inadequacy of its discoveries in the solids to
account for disease and death, has been compelled to seek for an
extension of its boundary through a direct examination of the
blood itself.' _Rokitansky's Pathological Anatomy_, vol. i. p.
362, London, 1854.

[828] Unless, as is the case in geometry, the premisses, which are
suppressed, are so slight as to be scarcely perceptible.

[829] He was so indignant at the bare idea of a humoral pathology, that
even Hoffmann, who before himself was the most eminent advocate of
solidism, fell under his displeasure for allowing some little
weight to the humoral doctrines. He says that Hoffmann 'has not
applied his fundamental doctrine so extensively as he might have
done; and he has everywhere intermixed an humoral pathology, as
incorrect and hypothetical as any other.' _Cullen's Works_, vol.
i. p. 410. At p. 470, 'I have, therefore, assumed the general
principles of Hoffmann. And, if I have rendered them more correct,
and more extensive in their application, and, _more particularly,
if I have avoided introducing the many hypothetical doctrines of
the Humoral Pathology which disfigured both his and all the other
systems that have hitherto prevailed_, I hope I shall be excused
for attempting a system, which, upon the whole, may appear new.'

Several of the views advocated by Cullen were taken from Hoffmann, and several of the facts from Gaubius; but that his pathology, considered as a whole, is essentially original, is evident from a certain unity of design which is inconsistent with extensive plagiarism, and which proves that he had thoroughly thought out his subject for himself. Without, however, stopping to inquire how much he borrowed from others, I will briefly indicate a few of the salient points of his system, in order to enable the reader to understand its general character.

According to Cullen, all the solids in the human body are either simple or vital. The simple solids retain, after death, the properties which they possessed during life. But the vital solids, which form the fundamental part of the nervous system, are marked by properties, which disappear directly death occurs.[830] Hence, the simple solids, having fewer functions than the vital, have also fewer diseases; and the maladies to which they are liable admit of easy classification.[831] The real difficulty lies in the vital solids, because on their peculiarities the whole nervous system depends, and nearly all disorders are immediately due to changes in them. Cullen, therefore, made the nervous system the basis of his pathology; and, in speculating on its functions, he assigned the chief place to an occult principle, which he termed the Animal Power, or Energy, of the brain.[832] This principle acted on the vital solids. When the principle worked well, the body was healthy; when it worked ill, the body was unhealthy. Since, then, the state of the vital solids was the main cause of disorder, and since the Energy of the brain was the main cause of the state of the vital solids, it became important to know what the influences were which acted on the Energy, because in them we should find the beginning of the series. Those influences were divided by Cullen into physical and mental. The physical were, heat, cold, and effluvia, the three most potent of the material disturbers of the human frame.[833] The mental influences, which excited the brain to act on the solids, were comprised under six different heads, namely, the will, the emotions, the appetites, the propensities, and, finally, the two great principles of habit and of imitation, on which he, with good reason, laid considerable stress.[834] In arguing from these mental causes, and in generalizing the relations between them and the sensations of the body, he, faithful to his favourite method, proceeded deductively from the metaphysical principles then in vogue, without inquiring inductively into their validity, such an induction being, he thought, no part of his duty.[835] He was too anxious to get on with his dialectic, to be interrupted by so trifling a matter as the truth or falsehood of the premisses on which the reason rested. What he did in the metaphysical part of his pathology, he also did in its physical part. Although the blood and the nerves are the two leading features of the human economy, he did not search into them by a separate induction; he subjected them neither to chemical experiments in order to learn their composition, nor to microscopic observations in order to learn their structure.[836] This is the more observable, because though we must admit that animal chemistry was then generally neglected, and that its real meaning was scarcely understood until the wonderful labours of Berzelius revealed its importance, still the microscope was ready to Cullen's hands; it having been invented a hundred and fifty years before he completed his pathology, and having been in common scientific use for about a hundred years. But his love of synthesis overcame him. His system is constructed by reasoning from general principles; and of that process, he certainly was a consummate master. Between the premisses and the conclusion, he hardly ever lets error creep in. And, in reference to the results of his speculations, he had one immense merit, which will always secure to him a conspicuous place in the history of pathology. By insisting on the importance of the solids, he, one-sided though he was, corrected the equal one-sidedness of his predecessors; for, with extremely few exceptions, all the best pathologists, from Galen downwards, had erred in ascribing too much to the fluids, and had upheld a purely humoral pathology. Cullen turned the minds of men in the other direction; and though, in teaching them that the nervous system is the sole primary seat of disease, he committed a great mistake, it was a mistake of the most salutary kind. By leaning on that side, he restored the balance. Hence, I have no doubt, he indirectly encouraged those minute researches into the nerves, which he would not himself stop to make, but which, in the next generation, gave rise to the capital discoveries of Bell, Shaw, Mayo, and Marshall Hall. At the same time, the old humoral pathology, which had prevailed for many centuries, was practically pernicious, because, assuming that all diseases are in the blood, it produced that constant and indiscriminate venesection, which destroyed innumerable lives, besides the irreparable injury it often inflicted both on body and mind; weakening those whom it was unable to slay. Against this merciless onslaught, which made medicine the curse of mankind, the Solid Pathology was the first effective barrier.[837] Practically, therefore, as well as speculatively, we must hail Cullen as a great benefactor of his species; and we must regard his appearance as an epoch in the history of human comfort, as well as in the history of human thought.

[830] 'The solid parts of the body seem to be of two kinds: one whose
properties are the same in the dead as in the living, and the same
in the animate as in many inanimate bodies; the other, whose
properties appear only in living bodies. In the last, a peculiar
organization, or addition, is supposed to take place; in
opposition to which the first are called the simple solids. Of
these only, we shall treat here; and of the others, which may be
called vital solids, being the fundamental part of the nervous
system, we shall treat under that title in the following section.'
_Cullen's Works_, vol. i. p. 10.

[831] These diseases are laxity, flaccidity, &c. See the enumeration of
'the diseases of the simple solids,' in _Cullen's Works_, vol. i.
p. 14.

[832] _Cullen's Works_, vol. i. pp. 65, 600, vol. ii. p. 364.
Dr. Thomson, who had access to papers and lectures of Cullen's,
which have never been published, says (_Life of Cullen_, vol. i.
p. 265), 'His speculations with regard to the different functions
of the nervous system, but more particularly with regard to that
of the Animal Power or Energy of the brain, were incorporated with
every opinion which he taught concerning the phenomena of the
animal economy, the causes of diseases, and the operation of
medicines; and they may be said to constitute a most important
part, if not the sole basis, of that system of the Practice of
Physic, which he made the subject of prelection, as well as of
study, for a period of nearly forty years, before he ventured to
give it to the public.' I should mention, that Cullen, under the
term 'brain,' included the contents of the vertebral column as
well as of the cranium.

[833] _Cullen's Works_, vol. i. pp. 40, 546, 558, 648, vol. ii. p. 321.

[834] _Cullen's Works_, vol. i. pp. 86, 91, 100, 101, 108, 115, 116,
553, 592, vol. ii. pp. 35, 366. Compare the summary of causes in
_Thomson's Life of Cullen_, vol. i. p. 289.

[835] He says (_Works_, vol. i. pp. 31, 32), 'Whoever has the smallest
tincture of metaphysics will know the distinction pointed at here
between the qualities of bodies as primary and secondary.' ...
'_Whether these distinctions be well or ill founded, it is not my
business to inquire._' But though he did not deem it his business
to inquire into the accuracy of these and similar distinctions, he
thought himself justified in assuming them, and reasoning from
them as if they could explain the working of those sensations,
whose perversion formed the point of contact between metaphysics
and pathology. See, for instance, in his _Works_, vol. i. p. 46,
the long series of unproved and improvable assertions respecting
the combination and comparison of sensations giving rise to
memory, imagination, and the like.

[836] Cullen, with that admirable candour which was one of the most
attractive peculiarities of his fine intellect, confesses his want
of acquaintance with the microscope: 'It leaves me, who am not
conversant in such observations, altogether uncertain with respect
to the precise nature of this part of the blood.' _Cullen's
Works_, vol. i. p. 195. A pathologist without a microscope is an
unarmed man, indeed. In regard to his animal chemistry, one
passage may be quoted as a specimen of the manner in which he
arrived at conclusions speculatively, instead of subjecting the
phenomena to experimental investigation. 'We may remark it to be
highly probable, that all animal matter is originally formed of
vegetable; because all animals either feed directly and entirely
on vegetables, or upon other animals that do so. From hence it is
probable, that all animal substances may be traced to a vegetable
origin; and _therefore_, if we would inquire into the production
of animal matter, we _must first inquire_ in what manner vegetable
matter may be converted into animal?' _Cullen's Works_, vol. i.
pp. 177, 178. The _therefore_ and the _must_, resulting merely
from an antecedent probability, are characteristic of that
over-boldness, into which deduction is apt to degenerate, and
which is strongly contrasted with the opposite vice of
over-timidity, by which inductive reasoners are tainted.

[837] Dr. Watson (_Principles and Practice of Physic_, 4th edit. London,
1857, vol. i. p. 41) says of the humoral pathology, that, 'the
absurdity of the hypothesis, and _still more the dangerous
practice which this doctrine generated_, began to be manifest, and
led to its total abandonment.' But, with every respect for this
eminent authority, I venture to observe, that this supposition of
Dr. Watson's is contradicted by the whole history of the human
mind. There is no well-attested case on record of any theory
having been abandoned, because it produced dangerous results. As
long as a theory is believed, men will ascribe its evil
consequences to any cause except the right one. And a theory which
is once established, will always be believed, until there is some
change in knowledge which shakes its foundation. Every practical
change may, by careful analysis, be shown to depend, in the first
instance, on some change of speculative opinions. Even at the
present day, many doctrines are generally held in the most
civilized countries, which are producing dangerous practical
consequences, and have produced those consequences for centuries.
But the mischief which the doctrine engenders does not weaken the
doctrine itself. Nothing can do that, but the general progress of
knowledge, which, by altering former opinions, modifies future
conduct.

It may, perhaps, facilitate the conceptions of unprofessional readers, if I give, in as few words as possible, a specimen of the way in which Cullen employed his method, in investigating the theory of some one class of diseases. For this purpose, I will select his doctrine of fever, which, though now generally abandoned, once exercised more influence than any other part of his pathology. Here, as elsewhere, he reasons from the solids.[838] Disregarding the state of the blood, he says, that the cause of all fever is a diminished energy of the brain.[839] Such diminution may be produced by various sedatives, the most common of which are effluvia, whether marsh or human, intemperance, fear, and cold.[840] Directly the energy of the brain is impaired, the disease begins. Rapidly passing through the nervous system, its first palpable effect is a chill, or cold fit, which is accompanied by a spasm on the extremities of the arteries, particularly where they touch the surface of the body.[841] This spasm on the extreme vessels, irritates the heart and arteries, and the irritation continues till the spasm is relaxed.[842] At the same time, the increased action of the heart restores the energy of the brain; the system rallies; the extreme vessels are relieved; while, as a consequence of the whole movement, sweat is excreted, and the fever abates.[843] Shutting out, therefore, all consideration of the fluids of the body, the successive stages of languor, cold fit, and hot fit, might, in Cullen's opinion, be generalized by reasoning merely from the solids, which, furthermore, produced his well-known distinction between fevers, the continuance of which is owing to an excess of spasm, and those, the continuance of which is owing to an excess of debility.[844]

[838] Some writers, who have taken notice of Cullen, have been deceived
in this respect by his occasional use of the expression 'nervous
fluid,' as if he were willing to let in the idea of humorism. But,
in one place, he distinctly guards himself against such
misconstruction. 'Now, to avoid determining any thing with regard
to these opinions, I have used the term of _nervous power_; but as
this is a little ambiguous, I choose to express it by _nervous
fluid_; not that I suppose, with Dr. Boerhaave, that the brain is
an excretory, and that a fluid is secreted from it: _I mean
nothing more than that there is a condition of the nerves which
fits them for the communication of motion_. But I defer the
consideration of these opinions for the present, and perhaps _ad
Græcas calendas_; but nothing shall be rested upon the nervous
fluid, it shall be considered merely as _a power_ fitted for
communicating motions.' _Cullen's Works_, vol. i. p. 17. Without
this passage, his remarks on 'the nervous fluid in the brain'
(_Works_, vol. i. p. 129), might easily be misunderstood.

[839] 'Together with this, the languor, inactivity, and debility of the
animal motions, the imperfect sensations, the feeling of cold,
while the body is truly warm, and some other symptoms, all show
that the energy of the brain is, on this occasion, greatly
weakened; and I presume that, as the weakness of the action of the
heart can hardly be imputed to any other cause, this weakness also
is a proof of the diminished energy of the brain. So I conclude,
that a debility of the nervous power forms the beginning of the
cold fit, and lays the foundation of all the other phenomena.'
_Practice of Physic_, in _Cullen's Works_, vol. i. p. 492.

[840] 'To render our doctrine of fever consistent and complete, it is
necessary to add here, that these remote causes of fever, human
and marsh effluvia, seem to be of a debilitating or sedative
quality.' ... 'Though we have endeavoured to show that fevers
generally arise from marsh or human effluvia, we cannot, with any
certainty, exclude some other remote causes, which are commonly
supposed to have at least a share in producing those diseases. And
I proceed, therefore, to inquire concerning these causes; the
first of which that merits attention, is the power of cold applied
to the human body.' ... 'Besides cold, there are other powers that
seem to be remote causes of fever; such as fear, intemperance in
drinking, excess in venery, and other circumstances, which
evidently weaken the system. But whether any of these sedative
powers be alone the remote cause of fever, or if they only operate
either as concurring with the operation of marsh or human
effluvia, or as giving an opportunity to the operation of cold,
are questions not to be positively answered.' _Practice of
Physic_, in _Cullen's Works_, vol. i. pp. 546, 552. One part of
this view has been corroborated, since the time of Cullen. 'The
experiments of Chossat and others clearly prove cold to be a
direct sedative.' _Williams' Principles of Medicine_, 2nd edit.
London, 1848, p. 11. Compare _Watson's Principles and Practice of
Physic_, 4th edit. London, 1857, vol. i. pp. 87-92, 249. Hence,
perhaps, the 'irresistible tendency to sleep caused by exposure to
severe or long-continued cold.' _Erichsen's Surgery_, 2nd edit.
London, 1857, p. 336; but as to this, Dr. Watson (_Principles of
Physic_, vol. i. p. 89) is sceptical, and thinks that, in those
cases which are recorded, the drowsiness ascribed to cold, is, in
a great measure, the result of fatigue.

[841] _Cullen's Works_, vol. i. p. 493. Compare, respecting his general
theory of spasm, p. 84, and vol. ii. p. 400.

[842] 'The idea of fever, then, may be, that a spasm of the extreme
vessels, however induced, proves an irritation to the heart and
arteries; and that this continues till the spasm is relaxed or
overcome.' _Cullen's Works_, vol. i. p. 494.

[843] 'Such, however, is, at the same time, the nature of the animal
economy, that this debility proves an indirect stimulus to the
sanguiferous system; whence, by the intervention of the cold stage
and spasm connected with it, the action of the heart and larger
arteries is increased, and continues so till it has had the effect
of restoring the energy of the brain, of extending this energy to
the extreme vessels, of restoring, therefore, their action, and
thereby especially overcoming the spasm affecting them; upon the
removing of which, the excretion of sweat, and other marks of the
relaxation of excretories, take place.' _Practice of Physic_, in
_Cullen's Works_, vol. i. pp. 501, 502. See also p. 636, § cciii.
Or, as he elsewhere expresses himself (vol. i. p. 561): 'With
regard to the event of fevers, this is the fundamental principle:
_in fevers, nature cures the disease_; that is, certain motions
tending to death continue the disease, but, in consequence of the
laws of the animal economy, other motions are excited by these
which have a tendency to remove it.'

[844] 'If we may trust to our conclusions with respect to the proximate
cause, it follows, most naturally, from the view there given, that
the continued fever is always owing to an excess of spasm, or to
an excess of debility: as the one or other of these prevails, it
will give one or other of the two forms, either the Synocha or
inflammatory fever, or the Typhus or nervous fever.' _Cullen's
Works_, vol. i. p. 518.

A similar process of thought gave birth to his _Nosology_, or general classification of diseases, which some have regarded as the most valuable part of his labours;[845] though, for reasons already mentioned, we must, I think, reject all such attempts as premature, and as likely to work more harm than good, unless they are simply used as a contrivance to aid the memory. At all events, the _Nosology_ of Cullen, though it exhibits clear traces of his powerful and organizing mind, is fast falling into disrepute, and we may be sure, that, for a long time yet, a similar fate will await its successors. Our pathological knowledge is still too young for so great an enterprise.[846] We have every reason to expect, that, with the aid of chemistry, and of the microscope, it will continue to grow more rapidly than it has hitherto done. Without venturing to predict the rate of its increase, we may form some idea of it, by considering what has been effected with resources very inferior to those we now possess. In a work of great authority, published in the year 1848, it is stated, that since the appearance of Cullen's _Nosology_, our mere enumeration of diseases has almost doubled, while our knowledge of the facts relating to disease has more than doubled.[847]

[845] 'Cullen's most esteemed work is his _Nosology_.' _Hamilton's
History of Medicine_, London, 1831, vol. ii. p. 279. 'His
_Nosology_ will probably survive all his other works; it is
indisputably the best system which has yet appeared.' _Lives of
British Physicians_, London, 1830, p. 213. 'Celle de Cullen, qui
parut en 1772, et qui constitue un véritable progrès.' _Renouard_,
_Histoire de la Médecine_, Paris, 1846, vol. ii. p. 231. See also
_Hooper's Medical Dictionary_, edited by Dr. Grant, London, 1848,
p. 937. But, in the most celebrated medical works which have
appeared in England during the last twelve or fifteen years, I
doubt if there is any instance of the adoption of Cullen's
nosological arrangement. Abroad, and particularly in Italy, it is
more valued.

[846] 'I had rather not be cramped and hampered by attempting what abler
heads than mine have failed to achieve, and what, in truth, I
believe, in the present state of our science, to be impossible, a
complete methodical system of nosology.' _Watson's Principles and
Practice of Physic_, London, 1857, vol. i. p. 9. This is the
wisdom of a powerful understanding.

[847] 'Now, when the diseases of Cullen's nosology have been almost
doubled, and the facts relating to them have been more than
doubled.' _Williams' Principles of Medicine_, London, 1848,
p. 522.

I have now only one more name to add to this splendid catalogue of the great Scotchmen of the eighteenth century.[848] But it is the name of a man, who, for comprehensive and original genius, comes immediately after Adam Smith, and must be placed far above any other philosopher whom Scotland has produced. I mean, of course, John Hunter, whose only fault was, an occasional obscurity, not merely of language, but also of thought. In this respect, and, perhaps, in this alone, Adam Smith had the advantage; for his mind was so flexible, and moved so freely, that even the vastest designs were unable to oppress it. With Hunter, on the contrary, it sometimes seemed as if the understanding was troubled by the grandeur of his own conceptions, and doubted what path it ought to take. He hesitated; the utterance of his intellect was indistinct.[849] Still, his powers were so extraordinary, that, among the great masters of organic science, he belongs, I apprehend, to the same rank as Aristotle, Harvey, and Bichat, and is somewhat superior either to Haller or Cuvier. As to this classification, men will differ, according to their different ideas of the nature of science, and, above all, according to the extent to which they appreciate the importance of philosophic method. It is from this latter point of view that I have, at present, to consider the character of John Hunter; and, in tracing the movements of his most remarkable mind, we shall find, that, in it, deduction and induction were more intimately united than in any other Scotch intellect, either of the seventeenth or eighteenth century. The causes of this unusual combination, I will now endeavour to ascertain. When they are understood, they will not only explain many peculiarities in his works, but will afford materials for speculation, to those who love to examine the development of ideas, and who are able to discern the way in which different schemes of national thought have given different shapes to national character, and have thereby modified the whole course of human affairs, to an extent of which the ordinary compilers of history have not the slightest suspicion.

[848] I had intended giving some account of the once celebrated
Brunonian system, which was founded by Dr. John Brown, who was
first the pupil of Cullen, and afterwards his rival. But a careful
perusal of his works has convinced me that the real basis of his
doctrine, or the point from which he started, was not pathology,
but therapeutics. His hasty division of all diseases into sthenic
and asthenic, has no claim to be deemed a scientific
generalization, but was a mere artificial arrangement, resulting
from a desire to substitute a stimulating treatment in the place
of the old lowering one. He, no doubt, went to the opposite
extreme; but that being a purely practical subject, this
Introduction has no concern with it. For the same reason, I omit
all mention of Currie, who, though an eminent therapeutician, was
a commonplace pathologist. That so poor and thinly-peopled a
country as Scotland, should, in so short a period, have produced
so many remarkable men, is extremely curious.

[849] Mr. Ottley (_Life of Hunter_, p. 186) says, 'In his writings we
occasionally find an obscurity in the expression of his thoughts,
a want of logical accuracy in his reasonings, and an incorrectness
in his language, resulting from a deficient education.' But, a
deficient education will never make a man obscure. Neither will a
good education make him lucid. The only cause of clearness of
expression is clearness of thought; and clearness of thought is a
natural gift, which the most finished and systematic culture can
but slightly improve. Uneducated men, without a thousandth part of
John Hunter's intellect, are often clear enough. On the other
hand, it as frequently happens that men, who have received an
excellent education, cannot speak or write ten consecutive
sentences which do not contain some troublesome ambiguity. In
Hunter's works such ambiguities are abundant; and this is probably
one of the reasons why no one has yet given a connected view of
his philosophy. On his obscurity, compare _Cooper's Life of Sir
Astley Cooper_, London, 1843, vol. i. pp. 151, 152; _Paget's
Lectures on Surgical Pathology_, London, 1853, vol. i. p. 419; and
the remarks of his enemy, Foot, in _Foot's Life of Hunter_,
London, 1794, p. 59.

Hunter remained in Scotland till the age of twenty, when he settled in London; and, though he was abroad for about three years, he abandoned his own country, and became, socially and intellectually, a native of England.[850] Hence, the early associations of his mind were formed in the midst of a deductive nation; the later associations, in the midst of an inductive one. For twenty years he lived among a people, who are, perhaps, the acutest reasoners in Europe, if you concede to them the principles from which they reason; but who, on the other hand, owing to their proneness to this method, are so greedy after general principles, that they will accept them on almost any evidence, and are, therefore, at once very credulous and very logical. In that school, and surrounded by those habits, the intellect of John Hunter was nurtured during the most impressible period of his life. Then the scene suddenly shifted. Coming to England, he passed forty years in the heart of the most empirical nation in Europe; a nation utterly abhorring all general principles, priding itself on its common sense, boasting, and with good reason too, of its practical sagacity, proclaiming aloud the superiority of facts over ideas, and despising every theory, unless some direct and immediate benefit could be expected to accrue from it. The young and ardent Scotchman found himself transplanted into a country totally different from that which he had just quitted; and such a difference could not fail to influence his mind. He saw, on every side, marks of prosperity, and of long and uninterrupted success, not only in practical, but also in speculative, life; and he was told that these things were effected by a system which made facts the first consideration. He was ambitious of fame, but he perceived that the road to fame was not the same in England as in Scotland. In Scotland, a great logician would be deemed a great man; in England, little account would be made of the beauty of his logic, unless he was careful that the premisses from which he argued, were trustworthy, and verified by experience. A new machine, a new experiment, the discovery of a salt, or of a bone, would, in England, receive a wider homage, than the most profound speculation from which no obvious results were apprehended. That this way of contemplating affairs has produced great good, is certain. But it is also certain, that it is a one-sided way, and satisfies only part of the human mind. Many of the noblest intellects crave for something which it cannot supply. In England, however, during the greater part of the eighteenth century, it was even more supreme than it is now, and was, indeed, so universal, that, from the year 1727 until nearly the close of the century, our country did not possess, in any branch of science, a speculator who had sufficient force to raise himself above those narrow views which were then deemed the perfection of wisdom.[851] Much was added to our knowledge, but its distant boundaries were not enlarged. Though there was an increase of curious and valuable details, and though several of the small and proximate laws of nature were generalized, it must be admitted, that those lofty generalizations, which we owe to the seventeenth century, remained stationary, and that no attempt was made to push beyond them. When John Hunter arrived in London, in 1748, Newton had been dead more than twenty years, and the English people, absorbed in practical pursuits, and now beginning, for the first time, to enter into political life, had become more averse than ever to inquiries which aimed at truth without regard to utility, and had accustomed themselves to value science chiefly for the sake of the direct and tangible benefit which they might hope to derive from it.

[850] He was born in 1728, and came to London in 1748. _Adams' Life of
John Hunter_, 2nd edit. London, 1818, pp. 20, 203. According to
Adams (pp. 30-35), he was abroad as surgeon in the English army
from 1761 to 1763; though, in _Foot's Life of Hunter_, London,
1794, p. 78, he is said to have returned to England in 1762. Mr.
Ottley says that he returned in 1763. _Ottley's Life of Hunter_,
p. 22, in vol. i. of _Hunter's Works_, edited by Palmer, London,
1835.

[851] See _Buckle's History of Civilization_, vol. ii. pp. 374, 375.

That Hunter must have been influenced by these circumstances, will be obvious to whoever considers how impossible it is for any single mind to escape from the pressure of contemporary opinion. But, inasmuch as all his early associations had inclined him in another direction, we perceive that, during his long residence in England, he was acted on by two conflicting forces. The country of his birth made him deductive; the country of his adoption made him inductive. As a Scotchman, he preferred reasoning from general principles to particular facts; as an inhabitant of England, he became inured to the opposite plan of reasoning from particular facts to general principles. In every country, men naturally give the first place to what is most valued. The English respect facts more than principles, and therefore begin with the facts. The Scotch consider principles as most important, and therefore begin with the principles. And, I make no doubt that one of the reasons why Hunter, in investigating a subject, is often obscure, is that, on such occasions, his mind was divided between these two hostile methods, and that, leaning sometimes to one and sometimes to the other, he was unable to determine which he should choose. The conflict darkened his understanding. Adam Smith, on the other hand, in common with all the great Scotchmen who remained in Scotland, was remarkably clear. He, like Hume, Black, and Cullen, never wavered in his method. These eminent men were not acted on by English influence. Of all the most illustrious Scotchmen of the eighteenth century, Hunter alone underwent that influence, and he alone displayed a certain hesitation and perplexity of thought, which seems unnatural to so great a mind, and which, as it appears to me, is best explained by the peculiar circumstances in which he was placed.