COMPARATIVE ANATOMY OF VERTEBRATA.* [SECOND NOTICE.]
THE history of the heresy as to the " fornix " in the marsupials resembles in many points the more familiar one of the " hippo- campi." For nearly thirty years the doctrine that the brain of the marsupials was as antipodally distinct from that of the ordi- nary mammal as its geographical distribution is, or as any other point in its habits or anatomy could be, was very generally accepted, and on the authority of a memoir of Professor Owen's. This difference was understood to lie in the fact that the " fornix" of these creatures had no "corpus callosum" to eke out its func- tions, and indeed only so lately as last year Professor Owen, in language apparently intended to exclude qualifying phrases, stated that this latter structure made " its appearance abruptly in the rats, shrews, bats, and sloths, which in general organiza- tion and powers are next the ' loose-brained' marsupials or lyen- cephala." It is true that in 1837, when this striking statement was Comparative Anatomy and Physiology of Vertebrates. By It:chard Owen, F.R.S. 2 Tula London : Lougmans. 1860. first put forth, it was qualified, or, as we should now say, nulli- fied, by the admission that the "corpus callosum" might, never- theless and notwithstanding, be considered to be present in the marsupial brain as a " rudimental commencement ;" but in those days, when the classificatory importance of rudimentary structures was little recognized, the naturalist was told he might safely use an anatomical inaccuracy for a zoological differentia. The qualify- ing statement, however, which we have just mentioned was shortly left to fall into oblivion ; and in 1857 the animals in question were called and classed as " lyencephala," " loose-brained" creatures, for that they lacked a " corpus callosum." So stood the matter till last year, when a third element of error was shown to exist in the doctrine of 1857, Professor Owen's successor at the College of Surgeons having demonstrated that a second portion of "corpus callosum," besides and beyond that which had been treated in such a step- fatherly fashion, was to be found and seen in those animals which had been classed apart, as being practically devoid of it altogether. The last publishedvolume of the Philosophical Transactions will show not only that Mr. Flower is scientifically correct, but also that he has represented his opponents' views fairly, and even gracefully; and it is therefore the more to be regretted that Professor Owen should have written as follows in the volume now before us (Vol. I., p. xix.). "Only by ignoring such indication of the ' rudimental commence- ment of the corpus callosum' may a semblance of superior know- ledge be assumed by him who asserts, as an antagonistic propo- sition to an affirmation of its absence as a zoological character, that the marsupialia, e. g., do possess the ' great cominissure ' or ' corpus callosum.' " Professor Owen could well have afforded to acknowledge an oversight in a field of research which owes so much to his labours; and the anatomical world would have thought as little of it as the traveller in the backwoods thinks of the stump still left unstubbed up in the primeval forest. That this is not the feeling of the world of experts, is owing to the line of defence which Professor Owen has chosen to take up.
Thirdly, we have six pages, xxi.-xxvi. of the preface in the first volume, devoted to the support of the astounding paradox that embryology is not a criterion of homology ;" and on the very last page but one, p. 585, of the second volume we find certain in- dubitable facts of " developmental phenomena" spoken of not as the most certain of all indications of the true relations of the parts they concern, but as " veritable will-o'-the-wisps to hunters of homologies on embryological ground." The very enunciation of these views carries with it their condemnation ; it is sufficient here to say that an application of the like principles to comparative philology instead of comparative anatomy would lead to the con- clusions that the study of Sanskrit was but a " will-o'-the-wisp" to the student of Bengali, that the natural history of the language of Zoroaater cast no trustworthy light on that of Firdusi, Ennins' none on that of Juvenal, Juvenal's none on that of Dante, Chaucer's none on that of Tennyson, and in short, that all that philology has concerned itself with, from the days of Samuel Johnson down to those of Max Muller, has been but a " hunting" of chimeras.
The origination of species Professor Owen believes to have been committed to certain natural laws or secondary causes, but of the mode of the operation of these causes he confesses himself to be in ignorance, and he speaks of Mr. Darwin's views, together with those of Lamarck, as " guess endeavours," p. xxxvi., Vol. I. But it is right to say that his utterances on this matter are somewhat ambiguous, and give forth a somewhat uncertain sound. We read, Vol. L, p. 6, Vol. H., p. 13, of birds being "genetically" or " derivatively" most closely connected with the extinct flying lizards; whilst we are told, Vol. H., p. 255, that how certain " arrangements in their eggs, in anticipatory relation to the needs and conditions of incubation, can be brought about by selection s or other operations of an unintelligent nature is not conceivable." And in the very page in which, Vol. L, p. xxxvi., the operation of the conditions of existence is declared to be inadequate to the production of a change in species, we have the following specula- tion as to our own species thrown down before us from the stand- point of the most advanced transmutationist. " In the lapse of ages hypothetically invoked for the mutation of specific distinc- tions, I would remark that man is not likely to preserve his longer than contemporary species theirs. Seeing the greater variety of influences to which he is subject, the present characters of the human kind are likely to be sooner changed than those of lower existing species." Of this perhaps we have no right to, complain, though it does seem a little like the behaviour of the Englishman who, when in Rome, always removed his hat as he passed any statue of Jupiter, to establish, as he said, a claim for favourable consideration in case of Paganism ever coining again into fashion. We have the hippocampal controversy revived both in the preface in the first volume, pp. xx. and xxxii., and in the intro- ductory chapter on "Mammals" in the second, p. 273. The history of this controversy is as follows :—At scientific and semi-scientific meetings a doctrine of Professor Owen's, to the effect that there existed in man's bodily organization, and specially in his cerebral system, certain distinguishing characteristics analogous to what are known in man's creations as "trade marks," whereby he could be at once, and easily, and sharply separated from all the lower animals, passed unquestioned for some years previously to the gathering together of the British Association at Oxford in 1860. These " trade-mark-like " structures were the third lobe of the cerebrum, the posterior horn of its lateral ventricle, and its " hippocampus minor." And this significance had been assigned to them by Professor Owen in the following words, to be found at pp. 19-20 of a paper published by him in the Linnaean Society's Proceedings for 1857, and referred to by him several times in the work now before us:—" The third lobe " is " peculiar to the genus Homo, and equally peculiar is the ' posterior horn of the lateral ventricle' and the hippocampus minor,' which characterize the hind lobe of each hemisphere." Certain quantitative, as opposed to qualitative, superiorities were, in the same connection, ascribed to the human cerebrum ; and it was declared with truth to project further in front, and, with some need of qualification, further back- wards also, than in the " villanously low " crania of the Apes. But these differences of size and quantity obtained much less popular currency than did the morphological ones above specified. They were much less easily recollected and repeated, and explanations must be easy and level to the comprehension of the crowd if they are to obtain a speedy and wide currency amongst that body. For this end it is of much less consequence whether they be adequate or not. A theory which gives the cause or the cure of a disease, or the explanation of some physiological riddle, in a single phrase, never fails to obtain a speedy and a wide, if not a lasting, currency and acceptance; and the doctrine which placed man's difference from the brute in the third horn of a lateral ventricle, and in its yet more easily recollected " hippocampus minor," was as speedily and widely accepted by the multitude as, we doubt not, it was thoroughly believed in by its promulgator. Professor Owen himself, it is true, 'had, in the very memoir from which we have just quoted, spoken strangely enough " of the deterraination of the difference between Homo and Pithecus" as " the anatomists' difficulty ;" and Linnaeus had, in days of less knowledge, preceded him by saying, " Nullum hactenus charac- terem eruere potui unde homo a simia dignoscatur." Now, though both these statements are simply overstatements, even as regards the flesh and brain of the two subjects of comparison, the obvious truth of which they are an all but equally obvious exagger- tion should have made even the multitude a little slow to accept "a determination of the difference" which, so far from being an " anatomists' difficulty," admits of being alluded to in the Water- Babies. As Professor Owen had, in the same pages, spoken of himself as "not being able to appreciate or conceive of the dis- tinction between the psychical phenomena of a chimpanzee and of a Boschisman, or of an Aztec with arrested brain-growth, as being of a nature so essential as to preclude a comparison between them, or as being other than a difference of degree," the satisfac- tion and applause with which the most orthodox of mankind were wont to listen to the reiteration of the claims of the quadrisyl- labic fragment of nerve substance in question seemed, to persons of antimaterialistic leanings, a little unreasonable. Such persons, not having accepted the philosophy of Cabanis, saw and heard with aversion man's dignity and position staked on the possession by him not of reason, faith, or conscience, but of these obscure nodules of neurine, and they-would have been nothing loath to hear of the discovery of some half-dozen more " hippocampi " in the brain of some newly discovered monkey than could be shown in the brain of the greatest of all philosophers who should, like Bentham and Gauss, be dissected. And, with these views, or rather feelings, some, though not all, of Professor Owen's opponents went to work. Some of them, as he curiously enough puts on record, photographed what they saw of these structures in the apes, some did not ; but the upshot and outcome of their researches has been that, so far from its being the fact that these structures are "peculiar to man," they exist, and beyond all question, and often in a condition of great development, in the order in which it had been unambiguously said they were absent and wanting. In these lower animals these structures were shown to vary from species to species, being in some more, in others less developed, in relation and comparison with their brethren and with man ; and, stranger still, it was shown that it had been long
ago known and only recently forgotten that this self-same " hippo- campus " and its " cornu " varied in much the same fashion within the single species man from individual to individual. With this there was an end of their classificatory importance.
It is explicable by a reference to certain conditions of mal-pre- servation, of mal-preparation, and occasionally also, we believe, of disease, how Professor Owen came to overlook the existence of these structures in the lower animals ; but it is not explicable how he can now, after what he himself calls " deluges " of recent descriptions and figures of these structures, speak of them as existing in the apes merely as " beginnings and indications ;" nor how he can claim that his words as spoken and as put out by him in authoritative print did allow of its being supposed that they did exist thus and there in the condition of rudiments nor, finally, how he can complain of having been misrepresented by the three of his opponents whose writings he stigmatizes, Vol. II., p. 273, as being severally " puerile," " ridiculous," and " dis- graceful." Battles are rarely won by the employment of hard words; and the value which is now set upon Professor Owen's alliance in this field of warfare may be judged of from the fact that in one of the books which have recently appeared in Scot- land on "Science and Christian Thought," the author, Professor Duns, when treating in his tenth chapter of man, the ape, and their respective brains, makes no allusion to the hippocampi, nor mention of the authority who gave them their short-lived notoriety.
In closing this review we must say that, these later " enterprises set off his head," Professor Owen has established a lasting claim upon the gratitude of English, and indeed of all other anatomists, by the extent of ground which he has covered in his long sustained labours. It is true that before he entered upon the vast field of research with which his name is connected, Cuvier's treatises had mapped out more or less accurately the entire realm of compara- tive anatomy ; and that the Ossemens Fossiles had already reared up " that stately and undecaying arch, along which students of all time will pass" from the world of living to that of extinct animals. Still, in the numerous volumes of the Hunterian catalogue, and in his innumerable memoirs on modern and on geological forms of life, Professor Owen has made contributions to biology which no advance in the science will ever rob of interest, value, and importance.