Chapter V (8)

One of the ablest of his commentators has justly observed, that his natural inclination was, to conjecture what the laws of nature were, and then reason from them, instead of reasoning to them by slow and gradual induction.[852] This process of deduction was, as I have shown, the favourite method of all Scotchmen, and, therefore, was precisely the course which we should have expected him to adopt. But, inasmuch as he was surrounded by the followers of Bacon,[853] this natural bias was warped, and a large part of his marvellous activity was employed in observations and experiments, such as no Scotch thinker, living in Scotland, would ever have engaged in. He himself declared, that thinking was his delight;[854] and there can be no doubt that, had he been differently situated, thinking would have been his principal pursuit. As it was, the industry with which he collected facts, is one of the most conspicuous features in his career. His researches covered the whole range of the animal kingdom, and were conducted with such untiring zeal, that he dissected upwards of five hundred different species, exclusive of dissections of different individuals, and exclusive, too, of dissections of a large number of plants.[855] The results were carefully arranged and stored up in that noble collection which he formed, and of the magnitude of which we may gain some idea from the statement, that, at his death, it contained upwards of ten thousand preparations illustrative of the phenomena of nature.[856] By this means, he became so intimately acquainted with the animal kingdom, that he made a vast number of discoveries, which, considered singly, are curious, but which, when put together, constitute an invaluable body of new truths. Of these, the most important are, the true nature of the circulation in crustacea and insects;[857] the organ of hearing in cephalopods;[858] the power possessed by mollusks of absorbing their shells;[859] the fact that bees do not collect wax, but secrete it;[860] the semicircular canals of the cetacea;[861] the lymphatics of birds;[862] and the air-cells in the bones of birds.[863] We are also assured, that he anticipated the recent discoveries respecting the embryo of the kangaroo;[864] and his published works prove, that, in the human subject, he discovered the muscularity of the arteries,[865] the muscularity of the iris,[866] and the digestion of the stomach after death by its own juice.[867] Although, in his time, animal chemistry was not yet raised to a system, and was consequently little heeded by physiologists, Hunter endeavoured, by its aid, to search out the qualities of the blood, so as to ascertain the properties of its constituents.[868] He also examined it in different stages of embryonic life, and by minutely tracking it through its periods of development, he made the capital discovery, that the red globules of the blood are formed later than its other components. His contemporaries, however, were so little alive to the importance of this great physiological truth, that it fell dead upon them, and, being forgotten, it was, about fifty years afterwards, rediscovered, and was announced, in 1832, as a law of nature which had just been brought to light.[869] This is one of many instances in the history of our knowledge, which proves how useless it is for a man to advance too far beyond the age in which he lives.[870] But Hunter, besides making the discovery, also saw its meaning. From it, he inferred that the function of the red globules is to minister to the strength of the system, rather than to its repair.[871] This is now universally admitted; but it was not admitted till long after his death. Its recognition is chiefly owing to the rapid advance of animal chemistry, and to improvements in the microscope. For, by the employment of these resources, it has become manifest, that the red globules, the respiratory process, the production of animal heat, and the energy of the locomotive organs, are but different parts of a single scheme.[872] Their connexion with each other is established, not only by a comparison of different species, but also by a comparison of different members of the same species. In human beings, for example, the locomotive and other animal functions are more active in persons of a sanguine temperament than in those of a lymphatic temperament; while, in sanguine temperaments, the globules are more numerous than in lymphatic ones. The knowledge of this fact we owe to Lecanu;[873] and to him we are also indebted for an analogous fact, corroborating the same view. He has shown, that the blood of women contains more water and fewer red globules than the blood of men;[874] so that here again we discern the relation between these globules and the energy of animal life. Inasmuch, however, as these researches were not made until many years after the death of Hunter, the coincidence between them and his speculative conclusions is a striking instance of his power of generalization, and of that unrivalled knowledge of comparative anatomy, which supplied him with materials from which, in spite of the backwardness of animal chemistry, he was able to draw an inference, which later and minuter researches have decisively verified.[875]

[852] 'He followed his natural inclination. He preferred the more
delusive, apparently the more direct, road, which has seduced so
many philosophers. He sought to arrive at the general laws of
nature at once by conjecture: rather than, by a close and detailed
study of her inferior operations, to ascend, step by step, through
a slow and gradual induction to those laws which govern her
general procedure.' Babington's Preface to Hunter's _Treatise on
the Venereal Disease_, in _Hunter's Works_, vol. ii. p. 129.
Compare the narrow and carping criticism in _Foot's Life of
Hunter_, p. 163.

[853] That I may not be suspected of exaggeration, I will quote what by
far the greatest of all the historians of medicine has said upon
this subject. 'La majorité des médecins qui prétendaient s'être
formés d'après Bâcon, n'avaient hérité de lui qu'une répugnance
invincible pour les hypothèses et les systèmes, une grande
vénération pour l'expérience, et un désir extrême de multiplier le
nombre des observations. Ce fut chez les Anglais que la méthode
empirique en médecine trouva le plus de partisans, et c'est
principalement aussi chez eux qu'elle s'est répandue jusqu'aux
temps les plus rapprochés de nous. Sa propagation y fut favorisée,
non-seulement par le profond respect que les Anglais continuent
toujours de porter à l'immortel chancelier, mais encore par la
haute importance que la nation entière attache au sens commun,
_common sense_, et elle y demeura l'ennemie irréconciliable de
tous les systèmes que ne reposent pas sur l'observation.'
_Sprengel, Histoire de la Médecine_, vol. v. p. 411, Paris, 1815.

[854] Clive says, 'Much as Mr. Hunter did, he thought still more. He has
often told me, his delight was, to think.' _Abernethy's Hunterian
Oration_, London, 1819, p. 26.

[855] Mr. Owen, in his interesting Preface to the fourth volume of
_Hunter's Works_, says (p. vii.), 'There is proof that Hunter
anatomized at least five hundred different species of animals,
exclusive of repeated dissections of different individuals of the
same species, besides the dissections of plants to a considerable
amount.'

[856] 'Some idea may be formed of Hunter's extraordinary diligence, by
the fact, that his museum contained, at the time of his death,
upwards of 10,000 preparations, illustrative of human and
comparative anatomy, physiology, and pathology, and natural
history.' _Weld's History of the Royal Society_, London, 1848,
vol. ii. p. 92.

[857] 'I have tested the conflicting evidence of these observers by
dissection of the heart in the lobster; and you will perceive by
this preparation that it is more complicated than even the Danish
naturalist supposed, and fully bears out the opinion of Hunter in
regard to the mixed nature of the circulation in the crustacea.'
_Owen's Lectures on the Comparative Anatomy and Physiology of the
Invertebrate Animals_, 2nd edit. London, 1855, p. 318. 'Cuvier,
misled by the anomalous diffused condition of the venous system,
supposed that there was no circulation of the blood in insects;
yet the dorsal vessel was too conspicuous a structure to be
overlooked. Such, however, was the authority of the great
anatomist, that the nature of the heart began to be doubted, and
the strangest functions to be attributed to it. Hunter, however,
who was prepared to appreciate the true state of the circulating
system in insects, by his discovery of the approximately diffused
and irregular structure of the veins in the crustacea, has
described, in his work on the blood, all the leading characters of
the circulation in insects as it is recognized by comparative
physiologists of the present day.' _Ibid._ p. 383. Compare
_Hunter's Essays and Observations on Natural History_, London,
1861, vol. i. p. 108.

[858] 'The class called Sepia has the organ of hearing, though somewhat
differently constructed from what it is in fishes.' _An Account of
the Organ of Hearing in Fishes_, in _Hunter's Works_, vol. iv. p.
294. At the bottom of the page Mr. Owen observes, in a note, 'This
is the first announcement of the existence of an organ of hearing
in the Cephalopoda.'

[859] 'Hunter discovered that the molluscous inhabitant of a shell had
the power of absorbing part of its dwelling.' _Owen's Lectures on
the Comparative Anatomy and Physiology of the Invertebrate
Animals_, London, 1855, p. 544. 'Every shell-fish has the power of
removing a part of its shell, so as to adapt the new and the old
together, which is not done by any mechanical power, but by
absorption.' _Anatomical Remarks on a New Marine Animal_, in
_Hunter's Works_, vol. iv. p. 469, edit. Palmer. In a note to this
passage, it is said, that 'the doctrine of the absorption of shell
has been lately' (_i.e._ in 1833) 'adduced as a new discovery.'

[860] 'His keen observation did not fail to detect several errors which
preceding naturalists had fallen into, especially with regard to
the formation of the wax, which he proved to be secreted, not
collected, by the animal.' _Ottley's Life of Hunter_, p. 122. 'The
wax is formed by the bees themselves; it may be called an external
secretion of oil, and I have found that it is formed between each
scale of the under side of the belly.' _Observations on Bees_, in
_Hunter's Works_, vol. iv. p. 433.

[861] 'In the terminating part there are a number of perforations into
the cochlea, and one into the semicircular canals, which afford a
passage to the different divisions of the auditory nerve.'
_Observations on the Structure and [OE]conomy of Whales_, in
_Hunter's Works_, vol. iv. pp. 383, 384. 'The semicircular canals
of the cetacea, described by Hunter in the paper on Whales, a
structure which Cuvier rightly states that Camper overlooked, but
incorrectly claims the discovery as his own.' Preface to vol. iv.
of _Hunter's Works_, p. xxi.

[862] Dr. Adams, in his somewhat hasty _Life of Hunter_, says (pp. 27,
28), 'Mr. Hewson always claimed the discovery of lymphatics in
birds.' But the truth is, that Hewson never claimed it. He says,
'It may be necessary to mention here, that the dispute between Dr.
Monro and me is, who first discovered the lacteals of birds? for
as to the lymphatics in their necks (mentioned in this gentleman's
note), these we both allow were discovered by Mr. John Hunter,
about ten years ago.' And, again, 'These lymphatics in the necks
of fowls were first discovered by Mr. John Hunter.' _Hewson's
Works_, edit. Gulliver (Sydenham Soc.), pp. 102, 145.

[863] _Hunter's Works_, vol. iv. pp. xxi. 176.

[864] 'See Nos. 3731, 3734, 3735, in the Physiological series of the
Hunterian Museum, in which there are evidences that Mr. Hunter had
anticipated most of the anatomical discoveries which have
subsequently been made upon the embryo of the Kangaroo.' _Rymer
Jones' Organization of the Animal Kingdom_, London, 1855, pp. 829,
830.

[865] 'The muscularity of arteries, of which John Hunter made
physiological proof, is now a matter of eyesight.' _Simon's
Pathology_, London, 1850, p. 69. 'To prove the muscularity of an
artery, it is only necessary to compare its action with that of
elastic substances.' ... 'When the various uses of arteries are
considered, such as their forming different parts of the body out
of the blood, their performing the different secretions, their
allowing at one time the blood to pass readily into the smaller
branches, as in blushing, and at another, preventing it
altogether, as in paleness from fear: and if to these we add the
power of producing a diseased increase of any or every part of the
body, we cannot but conclude that they are possessed of muscular
powers.' _Hunter's Works_, vol. iii. p. 157. See also vol. iv.
p. 254. Mr. Gulliver, in his edition of _Hewson's Works_, London,
1846, says (p. 125), that Hunter's 'experiments on the functions
of the arteries are supported by the latest and best observations
on their structure.'

[866] 'The fact of the muscularity of the iris, which is here presumed
from analogy by Mr. Hunter, has been since directly proved by the
observations of Bauer and Jacob (_Phil. Trans._ 1822), and
indirectly by Berzelius, who found that the iris possesses all the
chemical properties of muscle.' Palmer's note in _Hunter's Works_,
vol. iii. p. 146, London, 1837.

[867] _Adams' Life of Hunter_, pp. 59, 60, 245. _Hunter's Works_, vol. i.
p. 43, vol. iv. pp. 116-121. _Watson's Principles of Physic_,
vol. ii. p. 440.

[868] 'Hunter subjects the blood to both mechanical and chemical
analysis, and endeavours to determine the characteristic
properties of its different constituents.' Owen's Preface to vol.
iv. of _Hunter's Works_, p. xii. But this gives, perhaps, rather
too high an idea of his animal chemistry; for such was then the
miserable state of this extremely important branch of knowledge,
that he arrived at the conclusion that 'blood gives no analysis
excepting that of common animal matter.' _Principles of Surgery_,
chap. iii. in _Hunter's Works_, vol. i. p. 229.

[869] 'In seeking to determine the respective importance of the different
constituents of the blood, by the philosophical and most difficult
inquiry into their respective periods of formation in the
development of the embryo, Hunter made the interesting discovery
that the vessels of the embryo of a red-blooded animal circulated
in the first instance colourless blood, as in the invertebrate
animals. 'The red globules,' he observes, 'seemed to be formed
later in life than the other two constituents, for we see while
the chick is in the egg the heart beating, and it then contains a
transparent fluid before any red globules are formed, which fluid
we may suppose to be the serum and the lymph.' I well remember the
feelings of surprise with which I listened, while at Paris in
1832, to a memoir read before the Academy of Science, by MM.
Delpech and Coste, the object of which was the announcement of the
same fact as a novel and important discovery. The statement of the
French observers was received with all the consideration which its
importance justly merited, without its being suspected that our
great physiologist had, half a century before, embraced it, with
all its legitimate deductions, in the extended circle of his
investigations.' Owen's Preface to vol. iv. of _Hunter's Works_,
p. xiii.

[870] Indeed, if we may rely on the references recently given by Mr.
Gulliver, which, from his great general accuracy, there seems no
reason to question, the fact that the pale blood precedes the red,
was known even in the time of Glisson. See Gulliver's learned
edition of _Hewson's Works_, London, 1846, p. 222. But, to the
contemporaries of Glisson, such a fact was isolated, and
consequently useless. Nothing is valuable while it appears to
stand alone.

[871] 'From the above account, it appears that whatever may be their
utility in the machine, the red globules certainly are not of such
universal use as the coagulating lymph, since they are not to be
found in all animals, _nor so early in those that have them_; nor
are they pushed into the extreme arteries, where we must suppose
the coagulating lymph reaches; neither do they appear to be so
readily formed. This being the case, _we must conclude them not to
be the important part of the blood in contributing to growth,
repair, &c. Their use would seem to be connected with strength._'
_A Treatise on the Blood, Inflammation, and Gunshot Wounds_, in
_Hunter's Works_, vol. iii. p. 68. In another remarkable passage,
he touches on the possibility of an increase in the amount of red
globules being connected with an increase in the amount of heat.
'I will not pretend to determine how far this may assist in
keeping up the animal heat.' _Observations on the Structure and
[OE]conomy of Whales_, in _Hunter's Works_, vol. iv. p. 364.

[872] The evidence of this is collected in the notes to _Buckle's
History of Civilization_, vol. i. pp. 58-61.

[873] 'According to Lecanu, temperament has an influence upon the
composition of the blood. He infers from his analyses that the
blood of lymphatic persons is poorer in solid constituents, and
especially in blood corpuscules, than that of persons of
sanguineous temperament, while the quantity of albumen is much the
same in both.' _Simon's Animal Chemistry with reference to the
Physiology and Pathology of Man_, London, 1845, vol. i. p. 236.
Compare _Thomson's Chemistry of Animal Bodies_, Edinburgh, 1843,
p. 370.

[874] _Simon's Animal Chemistry_, vol. i. pp. 234, 235. Subsequent
experiments have confirmed this. 'The proportion of red globules
_dried_ to 1000 parts of blood, is in healthy males estimated at
127 parts by Andral and Gavarret; lower and higher figures have
been given by other analysts, but this probably is the result of
somewhat different modes of proceeding. _In females the proportion
of globules is lower._ Becquerel and Rodier make the difference to
be about 15 parts per 1000.' _Jones and Sieveking's Pathological
Anatomy_, London, 1854, p. 23. Hence, the greater specific gravity
of male blood. See the interesting results of Dr. Davy's
experiments in _Davy's Physiological and Anatomical Researches_,
London, 1839, vol. ii. p. 32.

[875] Hunter died in 1793. The researches of Lecanu were published in
1831.

Another, and still more remarkable proof of the extent to which
Hunter outstripped his own age, appears in the following passage,
which has just been published in his posthumous works, and in
which he anticipates the grandest and most suggestive of all the
ideas belonging to the physiology of the nineteenth century. 'If
we were capable of following the progress of increase of the
number of the parts of the most perfect animal, as they first
formed in succession, from the very first to its state of full
perfection, we should probably be able to compare it with some one
of the incomplete animals themselves, of every order of animals in
the Creation, being at no stage different from some of the
inferior orders. Or, in other words, if we were to take a series
of animals, from the more imperfect to the perfect, we should
probably find an imperfect animal, corresponding with some stage
of the most perfect.' _Essays and Observations by John Hunter,
being his Posthumous Papers_, London, 1861, vol. i. p. 203.

Having thus, by a comprehensive survey of the animal world, associated its remarkable faculty of movement with the state of its blood, Hunter turned his attention to another aspect of the question, and took into consideration the movements of the vegetable world, in the hope that, by comparing these two divisions of nature, he might detect some law, which, being common to both, should unite into one study all the principles of organic motion. Though he failed in this great undertaking, some of his generalizations are very suggestive, and well illustrate the power and grasp of his mind. Looking at the organic kingdom as a whole, he supposed that its capacity of action, both in animals and in vegetables, was of three kinds. The first kind, was the action of the individual upon the materials it already possessed; and this gave rise to growth, secretion, and other functions, in which the juice of the plant was equivalent to the blood of the animal.[876] The second kind of action had for its object to increase these materials; it was always excited by want, and its result was, to nourish and preserve the individual.[877] The third kind was entirely due to external causes, including the whole material world, all the phenomena of which were a stimulus to some kind of action.[878] By combining, in different ways, these different sources of motion, and by studying every incitement to action, first, in reference to one of the three great divisions just indicated, and, secondly, in reference to the _power_ of action, as distinguished from the _quantity_ of action,[879] Hunter believed that some fundamental truths might be obtained, if not by himself, at all events by his successors. For, he thought that, though animals can do many things which plants cannot, still, the immediate cause of action is in both cases the same.[880] In animals, there is more variety of motion, but in plants there is more real power. A horse is certainly far stronger than a man. Yet a small vine cannot only support, but can raise, a column of fluid five times higher than a horse can. Indeed, the power which a plant exercises of holding a leaf erect during an entire day, without pause and without fatigue, is an effort of astonishing vigour, and is one of many proofs, that a principle of compensation is at work, so that the same energy which, in the animal world, is weakened by being directed to many objects, is, in the vegetable world, strengthened by being concentrated on a few.[881]

[876] 'The natural salutary actions, arising from stimuli, take place
both in animals and vegetables, and may be divided into three
kinds. The first kind of action, or self-motion, is employed
simply in the economical operations, by which means the immediate
functions are carried on, and the necessary operations performed,
with the materials the animal or vegetable is in possession of,
such as growth, support, secretion, &c. The blood is disposed of
by the actions of the vessels, according to their specific
stimulus, producing all the above effects. The juices of a plant
are disposed of according to the different actions of the
sap-vessels, arising also from their specific stimulus, which is
different from that of blood-vessels, but equally produces growth;
but a vine will grow twenty feet in one summer, while a whale,
probably, does not grow so much in as many years.' _Croonian
Lectures on Muscular Motion_, in _Hunter's Works_, vol. iv.
p. 199.

[877] 'The second kind of action is in pursuit of external influence, and
arises from a compound of internal and external stimulus; it is
excited by the state of the animal or vegetable, which gives the
stimulus of want, and being completed by external stimulus,
produces the proper supplies of nourishment. It produces motions
of whole parts: thus we see the _Hedysarum gyrans_ moving its
lesser foliola. This is an action apparently similar to breathing
in animals, though, perhaps, it does not answer the same purpose;
yet there is an alternate motion in both.' _Croonian Lectures_, in
_Hunter's Works_, vol. iv. p. 200.

[878] 'The third kind of motion is from external stimulus, and consists
principally of the motion of whole parts, which is not
inconsiderable in vegetables, as in the _Dionæa muscipula_ and
_Mimosa pudica_ is very evident.' ... 'These actions are similar
to what arise in many animals from external stimulus.' _Ibid._
vol. iv. p. 201.

[879] 'I make a material difference between the power and the quantity of
action. Some motions may be very small, yet act with great force;
while others are of considerable extent, although very weak.'
_Ibid._ vol. iv. p. 204.

[880] 'The immediate cause of motion in all vegetables is most probably
the same, and it is probably the same in all animals; but how far
they are the same in both classes, has not yet been determined.
But I think it will appear, in the investigation of this subject,
that vegetables and animals have actions evidently common to both,
and that the causes of these actions are apparently the same in
both; and most probably there is not an action in the vegetable,
which does not correspond or belong to the animal, although the
mode of action in the parts may not be the same, or muscular, in
both.' _Croonian Lectures_, in _Hunter's Works_, vol. iv. p. 196.
Compare the section 'Of Motion in Vegetables,' in _Hunter's
Essays_, London, 1861, vol. i. p. 24.

[881] 'The variety of motions is greater in animals, and more purposes
are answered by them.' ... 'The first kind of action appears to be
stronger in its power, although less in quantity, in vegetables
than in animals; for a small vine was capable of sustaining, and
even of raising, a column of sap 43 feet high, while a horse's
heart was only capable of supporting a column of blood 8 feet 9
inches high; both of which columns must have been supported by the
action of the internal parts, for we must suppose the heart equal,
or nearly so, to the strength or action of the other parts of the
vascular system; and when we consider that the sap of the tallest
tree must be supported, and even raised from the root to the most
distant branches, it must appear that the power of such vegetables
far exceeds the power of any animal, and, indeed, it is such as
the texture of a vegetable only can support. The power of
supporting a leaf erect for a whole day is as great an effort of
action as that of the elevator palpebrarum muscle of the eye of an
animal.' _Hunter's Works_, vol. iv. pp. 203, 204. See also
_Hunter's Essays_, vol. i. p. 342: 'It is probable that the
vegetable which can the least bear a suspension of its actions,
can do so more than the animal which can bear it longest.'

In pursuing these speculations, which, amid much that is uncertain, contain, I firmly believe, a large amount of important, though neglected, truth, Hunter was led to consider how motion is produced by various forces, such as magnetism, electricity, gravitation, and chemical attraction.[882] This carried him into inorganic science, where, as he clearly saw, the foundation of all organic science must be laid. Just as, on the one hand, the human frame could never be successfully studied, except by the aid of principles which had been collected from an investigation of animals below man,[883] so, on the other hand, the laws of those very animals must, he said, be approached through the laws of common or inorganic matter.[884] He, therefore, aimed at nothing less than to unite all the branches of physical science, taking them in the order of their relative complexity, and proceeding from the simplest to the most intricate. With this view, he examined the structure of the mineral kingdom, and, by an extensive comparison of crystals, he sought to generalize the principles of form, in the same way as, by a comparison of animals, he sought to generalize the principles of function. And, in doing this, he took into account, not only regular crystals, but also irregular ones.[885] For, he knew that, in nature, nothing is really irregular or disorderly; though our imperfect apprehension, or rather the backwardness of our knowledge, prevents us from discerning the symmetry of the universal scheme. The beauty of the plan, and the necessity of the sequence, are not always perceptible. Hence, we are too apt to fancy that the chain is broken, because we cannot see every link in it. From this serious error, Hunter was saved by his genius, even more than by his knowledge. Being satisfied that every thing which happens in the material world, is so connected and bound up with its antecedents, as to be the inevitable result of what had previously occurred, he looked with a true philosophical eye at the strangest and most capricious shapes, because to him they had a meaning and a necessary purpose. To him, they were neither strange nor capricious. They were deviations from the natural course; but it was a fundamental tenet of his philosophy, that nature, even in the midst of her deviations, still retains her regularity.[886] Or, as he elsewhere expresses it, deviation is, under certain circumstances, part of the law of nature.[887]

[882] _Hunter's Works_, vol. iv. p. 255.

[883] In his _Principles of Surgery_, he says (_Hunter's Works_, vol. i.
p. 220), 'The human body is what I mean chiefly to treat of; but I
shall often find it necessary to illustrate some of the
propositions which I shall lay down from animals of an inferior
order, in whom the principles may be more distinct and less
blended with others, or where the parts are differently
constructed, in order to show, from many varieties of structure,
and from many different considerations, what are the uses of the
same parts in man; or, at least, to show that they are not for the
uses which have been commonly assigned to them; and, as man is the
most complicated part of the whole animal creation, it will be
proper, in the first place, to point out general principles,
common to all this species of matter, that I may be better
understood when I come to the more complicated machine, namely,
the human.'

[884] 'Before we endeavour to give an idea of an animal, it is necessary
to understand the properties of that matter of which an animal is
composed; but the better to understand animal matter, it is
necessary to understand the properties of common matter; else we
shall be often applying our ideas of common matter, which are
familiar to us, to animal matter, an error hitherto too common,
but which we should carefully avoid.' _Principles of Surgery_, in
_Hunter's Works_, vol. i. p. 211. 'In the natural history of
vegetables and animals, therefore, it will be necessary to go back
to the first or common matter of this globe, and give its general
properties; then see how far these properties are introduced into
the vegetable and animal operations; or rather, perhaps, how far
they are of use or subservient to their actions.' _Hunter's
Essays_, vol. i. p. 4. 'Every property in man is similar to some
property, either in another animal, or probably in a vegetable, or
even in inanimate matter. Thereby (man) becomes classible with
those in some of his parts.' _Ibid._ p. 10.

[885] He made 'a valuable collection of crystallizations, both of
regular and irregular forms, which he was accustomed to use in his
lectures to exemplify the difference between the laws which
regulate the growth of organic and the increase of inorganic
bodies.' _Ottley's Life of Hunter_, p. 138.

[886] 'Nature is always uniform in her operations, and when she deviates
is still regular in her deviations.' _Principles of Surgery_, in
_Hunter's Works_, vol. i. p. 485; see also vol. iv. pp. 44, 45.

[887] 'It certainly may be laid down, as one of the principles or laws
of nature, to deviate under certain circumstances.' _Hunter's
Works_, vol. iv. p. 278.

To generalize such irregularities, or, in other words, to show that they are not irregularities at all, was the main object of Hunter's life, and was the noblest part of his mission. Hence, notwithstanding his vast achievements in physiology, his favourite pursuit was pathology,[888] where, the phenomena being more complex, the intellect has more play. In this great field, he studied the aberrations of structure and of function, in the vegetable, as well as in the animal, world;[889] while, for the aberrations of form, which are the external manifestations of disturbed structure, he took into consideration the appearances presented by the mineral kingdom. There, the power of crystallization is the leading feature, and there, violations of symmetry constitute the essential disorder, whether the deformity of the crystal is subsequent to its production, or whether, being the result of what happened before its production, it is an original, and, if we may so say, congenital, defect. In either case, it is a deviation from the normal type, and, as such, is analogous to the monstrosities, both of animals and of vegetables.[890] The mind of Hunter, by sweeping through this immense range of thought, attained to such commanding views of the philosophy of disease, that, in that department, he is certainly without a rival. As a physiologist, he was equalled, or perhaps excelled, by Aristotle; but as a pathologist, he stands alone, if we consider what pathology was when he found it, and what it was when he left it.[891] Since his death, the rapid advance of morbid anatomy and of chemistry has caused some of his doctrines to be modified, and some of them to be overturned. This has been the work of inferior men, wielding superior chemical and microscopical resources. To say that the successors of John Hunter are inferior to him, is no disparagement to their abilities, since he was one of those extremely rare characters who only appear at very long intervals, and who, when they do appear, remodel the fabric of knowledge. They revolutionize our modes of thought; they stir up the intellect to insurrection; they are the rebels and demagogues of science. And though the pathologists of the nineteenth century have chosen a humbler path, this must not blind us to their merits, or prevent us from being grateful for what they have done. We cannot, however, be too often reminded, that the really great men, and those who are the sole permanent benefactors of their species, are not the great experimenters, nor the great observers, nor the great readers, nor the great scholars, but the great thinkers. Thought is the creator and vivifier of all human affairs. Actions, facts, and external manifestations of every kind, often triumph for a while; but it is the progress of ideas which ultimately determines the progress of the world. Unless these are changed, every other change is superficial, and every improvement is precarious. It is, however, evident that, in the present state of our knowledge, all ideas respecting nature must refer either to the normal or to the abnormal; that is to say, they must be concerned either with what is regular, uniform, and obedient to recognized principles, or else with what is irregular, perturbed, and disobedient. Of these two divisions, the first belongs to science; the second, to superstition. John Hunter formed the superb conception of merging both classes of ideas into one, by showing that nothing is irregular, that nothing is perturbed, that nothing is disobedient. Centuries, perhaps, may elapse before that conception will be consummated. But what Hunter effected towards it, places him at the head of all pathologists, ancient or modern. For, with him, the science of pathology did not mean the laws of disease in man alone, or even in all animals, or even in the whole organic kingdom; but it meant the laws of disease and of malformation in the entire material world, organic and inorganic. His great object was, to raise a science of the abnormal. He determined to contemplate nature as a vast and united whole, exhibiting, indeed, at different times different appearances, but preserving, amidst every change, a principle of uniform and uninterrupted order, admitting of no deviation, undergoing no disturbance, and presenting no real irregularity, albeit to the common eye, irregularities abound on every side.

[888] Dr. Adams, who knew him personally, says that he studied
'physiology, more particularly as connected with pathology.'
_Adams' Life of Hunter_, p. 77.

[889] His _Principles of Surgery_ contain some curious evidence of his
desire to establish a connexion between animal and vegetable
pathology. See, for instance, his remarks on 'local diseases'
(_Works_, vol. i. p. 341); on the influence of the seasons in
producing diseases (vol. i. pp. 345, 346); and on the theory of
inflammation exhibited in an oak-leaf (vol. i. p. 391). But even
now, too little is known of the diseases of the vegetable world to
enable their study to be incorporated with the science of the
diseases of the animal world; and, in the time of Hunter, the
attempt was still less promising. Still, the effort shows the
grandeur and range of the man's mind; and though little was
effected, the method was right. So, too, in one of his essays on
the _Power of Producing Heat_, he says, 'In the course of a
variety of experiments on animals and vegetables, I have
frequently observed that the result of experiments in the one has
explained the economy of the other, and pointed out some principle
common to both.' _Hunter's Works_, vol. iv. p. 136.

[890] 'Nature being pretty constant in the kind and number of the
different parts peculiar to each species of animal, as also in the
situation, formation, and construction of such parts, we call
every thing that deviates from that uniformity a "monster,"
whether (it occur in) crystallization, vegetation, or
animalization. There must be some principle for those deviations
from the regular course of nature, in the economy of such species
as they occur in. In the present inquiry it is the animal creation
I mean to consider. Yet, as there may be in some degree an analogy
between all the three (kingdoms of nature), I shall consider the
other two, so far as this analogy seems to take place.' ...
'Monsters are not peculiar to animals: they are less so in them,
perhaps, than in any species of matter. The vegetable (kingdom)
abounds with monsters; and perhaps the uncommon formation of many
crystals may be brought within the same species of production, and
accounted for upon the same principle, viz. some influence
interfering with the established law of regular formation.
Monsters in crystals may arise from the same cause, as mentioned
in the "Introduction;" viz. either a wrong arrangement of the
parts of which the crystal is to be composed, or a defect in the
formation, from the first setting out being wrong, and (the
formation) going on in the same (wrong) line. The principle of
crystallization is in the solution; yet it requires more to set it
agoing, or into action, such, _e.g._, as a solid surface. The
deficiency in the production of a true crystal may be in the
solution itself; or, I can conceive, that a very slight
circumstance might alter the form of a crystal, and even give the
disposition for one (crystal) to form upon another. Quickness in
the progress of crystallization produces irregularity and
diminution in size.' _Hunter's Essays_, London, 1861, vol. i.
pp. 239-241. The reader must remember, that, when these remarks
were written, the phenomena of crystallization had not been
subjected to that exact mathematical treatment which subsequently
revealed so many of their laws. Indeed, the goniometer was then so
coarse an instrument, that it was impossible to measure the angles
of crystals with accuracy.

[891] Abernethy says, 'He appears to me as a new character in our
profession; and, briefly to express his peculiar merit, I may call
him the first and great physionosologist, or expositor of the
nature of disease.' _Abernethy's Hunterian Oration_, p. 29,
London, 1819. 'He may be regarded as the first who applied the
great truths of anatomical and physiological science to these most
important subjects, by tracing the processes which nature employs
in the construction of organic changes, in building up new
formations, and in repairing the effects of injury or disease.'
_Hodgson's Hunterian Oration_, 1855, p. 32.

As pathology was the science to which Hunter was most devoted, so also was it that in which his natural love of deduction was most apparent. Here, far more than in his physiological inquiries, do we find a desire to multiply original principles from which he could reason; in opposition to the inductive method, which always aims at diminishing these principles by gradual and successive analysis. Thus, for instance, in his animal pathology, he attempted to introduce, as an ultimate principle from which he could argue, the idea that all diseases move more rapidly towards the skin than towards internal parts, by virtue of some hidden force, which also obliges vegetables to approach the surface of the earth.[892] Another favourite proposition, which he often used as a major premiss, and by its aid constructed deductively a pathological argument, was, that in no substance, be it what it may, can two processes go on in the same part at the same time.[893] By applying this universal proposition to the more limited phenomena of animal life, he inferred that two general diseases cannot co-exist in the same individual; and he relied so much on this ratiocination, that he refused to credit any testimony by which it was impugned.[894] There is reason to believe that his conclusion is erroneous, and that different diseases can so accompany each other, as to be united in the same individual, at the same time, and in the same part.[895] Whether or not this be the case, it is equally interesting to notice the process of thought which led Hunter to bestow infinitely more pains in arguing from the general theory, than in arguing to it. Indeed, he can hardly be said to have argued to it at all, since he obtained it by a rough and hasty generalization from what seemed to be the obvious properties of inorganic matter. Having thus obtained it, he applied it to the pathological phenomena of the organic world, and especially of the animal world. That he should have adopted this course, is a curious proof of the energy of his deductive habits, and of the force of mind which enabled him so to set at naught the traditions of his English contemporaries, as to follow a method which, in the opinion of every one who surrounded him, was not only full of danger, but could never lead to truth.

[892] 'The specific qualities in diseases also tend more rapidly to the
skin than to the deeper-seated parts, except the cancer; although,
even in this disease, the progress towards the superficies is more
quick than its progress towards the centre.' ... 'In short, this
is a law of nature, and it probably is upon the same principle by
which vegetables always approach the surface of the earth.' _A
Treatise on the Blood, Inflammation, and Gunshot Wounds_, in
_Hunter's Works_, vol. iii. p. 285. 'Granulations always tend to
the skin, which is exactly similar to vegetation, for plants
always grow from the centre of the earth towards the surface; and
this principle was taken notice of when we were treating of
abscesses coming towards the skin.' _Ibid._ pp. 489, 490.

[893] 'It may be admitted as an axiom, that two processes cannot go on
at the same time in the same part of any substance.' _Hunter's
Works_, vol. iv. p. 96. Compare _Hunter's Essays_, vol. ii. p.
333: 'As it appears, in general, that Nature can hardly make one
part perform two actions with advantage.'

[894] 'Thus, we hear of pocky itch and of scurvy and the venereal
disease combined; but this supposition appears to me to be founded
in error. I have never seen any such cases, _nor do they seem to
be consistent with the principles of morbid action_ in the animal
economy. It appears to me beyond a doubt that no two actions can
take place in the same constitution, or in the same part, at one
and the same time.' _Hunter's Works_, vol. ii. p. 132. 'As I
reckon every operation in the body an action, whether universal or
partial, _it appears to me beyond a doubt_ that no two actions can
take place in the same constitution, nor in the same part, at one
and the same time; the operations of the body are similar in this
respect to actions or motions in common matter. _It naturally
results from this principle_, that no two different fevers can
exist in the same constitution, nor two local diseases in the same
part, at the same time. There are many local diseases which have
dispositions totally different, but having very similar
appearances, have been supposed by some to be one sort of disease,
by others to be a different kind, and by others again a compound
of two diseases.' ... 'These, therefore, are often supposed to be
mixed, and to exist in the same part. Thus we hear of a
pocky-scurvy, a pocky-itch, rheumatic-gout, &c. &c., which names,
_according to my principle_, imply a union that cannot possibly
exist.' _Ibid._ vol. iii. pp. 3, 4.

[895] Dr. Robert Williams (_Encyclopædia of the Medical Sciences_,
London, 1847, 4to, p. 688) says, 'The diagnosis between gout and
rheumatism is often exceedingly difficult, so much so that
nosologists have given a mixed class, or rheumatic gout. Mr.
Hunter warmly opposed this compound appellation, for, in his
opinion, no two distinct diseases, or even distinct diatheses, can
co-exist in the same constitution; a law, it must be admitted, to
have many exceptions.' Compare _Watson's Principles and Practice
of Physic_, London, 1857, vol. i. p. 312; 'acting upon the
aphorism of John Hunter (an aphorism, however, which requires some
qualification), that two diseases or actions cannot go on in a
part at the same time.' According to another authority, 'There can
be little doubt that two or more zymotic processes do often go on
simultaneously in the blood and body; a fact of profound interest
to the pathologist, and worthy of attentive investigation.'
_Report on the Public Health for 1847_, in _Journal of the
Statistical Society_, vol. xi. p. 168, London, 1848. See also, on
the co-existence of specific poisons, _Erichsen's Surgery_, 2nd
edit., London, 1857, p. 430. Mr. Paget, in his striking and
eminently suggestive _Lectures on Pathology_, London, 1853, vol.
ii. pp. 537, 538, has made some interesting remarks on one part of
the theory of co-existence; and his observations, so far as they
go, tend to corroborate Hunter's view. He has put very forcibly
the antagonism between cancer and other specific diseases; and
especially between the cancerous diathesis and the tuberculous.

Other parts of his pathology abound with similar instances, which show how anxious he was to assume principles on which he could build arguments. Of this kind were his ideas respecting sympathy, as connected with action. He suggested, that the simplest forms of sympathy would probably be found in the vegetable world, because there, the general arrangements are less intricate than in the animal world.[896] On this supposition, he constructed a series of curious and refined speculations, of which, however, I must confine myself to giving a very short summary. As animals sympathize more than vegetables, this helps us to understand why it is that their movements are more numerous. For, sympathy, being a susceptibility to impression, is also a principle of action.[897] Like other principles of action, it may be either natural or diseased.[898] But, whichever it be, it can, in plants, have only one mode of development, because, in them, it can only be influenced by stimulus; while in animals, which have sensation, it has necessarily three modes, one from stimulus, one from sensation, and a third compounded of the other two.[899] These are the largest divisions of sympathy, if we consider the organic world as a whole. In single cases, however, sympathy admits of still further subdivision. We may reason from it, in reference to the age of the individual;[900] we may also reason from it in reference to temperament, since, in point of fact, temperament is nothing but susceptibility to action.[901] And when sympathy is in action, we may, by analyzing our idea of it, reduce it to five different heads, and may classify it as continued, or contiguous, or remote, or similar, or dissimilar.[902] All these supplied Hunter with principles from which, by reasoning deductively, he attempted to explain the facts of disease; for, according to him, disease merely consists in a want of combination of actions.[903] By this process of thought, he was induced to neglect those predisposing causes, to which inductive pathologists pay great attention, and with which the works of his English contemporaries were much occupied. Such causes could only be generalized from observation, and Hunter made no account of them. Indeed, he even denies their real existence, and asserts that a predisposing cause is simply an increased susceptibility to form disposition to action.[904]

[896] 'The most simple sympathy is perhaps to be found in vegetables,
these being much more simple than the most simple animal.'
_Principles of Surgery_, in _Hunter's Works_, vol. i. p. 327.

[897] 'This principle of action, called sympathy,' &c. _Ibid._ vol. i.
p. 318.

[898] 'Sympathy may be divided into two kinds, the natural and the
diseased.' _Principles of Surgery_, in _Hunter's Works_, vol. i.
p. 320; see also _A Treatise on the Blood, Inflammation, &c._, in
_Works_, vol. iii. p. 6.

[899] _Croonian Lectures on Muscular Motion_, in _Hunter's Works_,
vol. iv. p. 207; and exactly the same words in his _Phytology_, in
_Hunter's Essays_, London, 1861, vol. i. p. 361.

[900] 'Local or partial sympathy is found more in old than in young;
whereas universal sympathy is more in young than in old. Sympathy
is less determined in young persons, every part being then ready
to sympathize with other parts under disease.' ... 'As the child
advances, the power of sympathy becomes partial, there not being
now, in the constitution, that universal consent of parts, but
some part, which has greater sympathy than the rest, falls into
the whole irritation; therefore the whole disposition to sympathy
is directed to some particular part. The different organs acquire
more and more of their own independent actions as the child grows
older.' _Hunter's Works_, vol. i. pp. 322, 323.

[901] 'Susceptibilities for dispositions and actions appear to me to be
the same with what are usually understood by temperament.
Temperament is the state of the body fitting it for the
disposition or action it is then in.' _Hunter's Works_, vol. i.
p. 307.

[902] _Hunter's Works_, vol. iii. p. 393.

[903] 'As every natural action of the body depends, for its perfection,
on a number of circumstances, we are led to conclude, that all the
various combining actions are established while the body is in
health, and well disposed; but this does not take place in
diseased actions, for disease, on the contrary, consists in the
want of this very combination.' _Hunter's Works_, vol. iii. p. 10.
Compare vol. i. p. 310: 'I have explained that a disease is a
disposition for a wrong action, and that the action is the
immediate effect of the disposition, and that either the actions
or the effects of those actions, _produce the symptoms which are
generally called the disease_; such as sensations, which are
commonly pain of all kinds, sickness, alteration visible or
invisible in the structure of the part or parts that act, and
sympathy.'

[904] 'There is no such thing, strictly speaking, as a predisposing
cause. What is commonly understood by a predisposing cause is an
increased susceptibility to form disposition to action. When I say
I am predisposed for such and such actions, it is only that I am
very susceptible of such and such impressions.' _Hunter's Works_,
vol. i. p. 303. See also p. 301: 'The most simple idea I can form
of an animal being capable of disease is, that every animal is
endued with a power of action, and a susceptibility of impression,
which impression forms a disposition, which disposition may
produce action, which action becomes the immediate sign of the
disease; all of which will be according to the nature of the
impression and of the part impressed.'