In July 1861 Mr. Marshall, in a paper on the brain of a young Chimpanzee, which he had dissected immediately after its death, gave a series of photographic drawings, showing that when the parts are all in a fresh state, the posterior lobe of the cerebrum, instead of simply covering the cerebellum, is prolonged backwards beyond it even to a greater extent than in Gratiolet's figure, 56, and, what is more in point, in a greater degree relatively speaking (at least in the young state of the animal) than in Man. In fact, "the projection is to the extent of about one-ninth of the total length of the cerebrum, whereas the average excess of overlapping is only one-eleventh in the human brain."*

(* Marshall, "Natural History Review" July 1861. See also on this subject Professor Rolleston on the slight degree of backward extension of the cerebrum in some races of Man.

"Medical Times" October 1862, page 419.)

The same author gives an instructive account of the manner in which displacement and distortion take place when such brains are preserved in spirits as in the ordinary preparations of the anatomist.

Mr. Flower, in a recent paper on the posterior lobe of the cerebrum in the Quadrumana,* remarks, that although Tiedemann had declared himself unable in 1821 to detect the hippocampus minor or the posterior cornu of the lateral ventricle in the brain of a Macacus dissected by him, Cuvier, nevertheless, mentions the latter as characteristic of Man and the apes, and M. Serres in his well-known work on the brain in 1826, has shown in at least four species of apes the presence of both the hippocampus minor and the posterior cornu.

(* "Philosophical Transactions" 1862 page 185.)

Tiedemann had expressly stated that "the third or hinder lobe in the ape covered the cerebellum as in Man,"* and as to his negative evidence in respect to the internal structure of that lobe, it can have no weight whatever against the positive proofs obtained to the contrary by a host of able observers. Even before Tiedemann's work was published, Kuhl had dissected, in 1820, the brain of the spider-monkey (Ateles beelzebuth), and had given a figure of a long posterior cornu to the lateral ventricle, which he had described as such.**

(* Tiedemann, "Icones cerebri Simiarum" etc. page 48.)

(** "Beitrage zur Zoologie" etc. Frankfurt am Main 1820.)

The general results arrived at by the English anatomists already cited, and by Professor Rolleston in various papers on the same subject, have thus been briefly stated by Professor Huxley:--

"Every lemur which has yet been examined has its cerebellum partially visible from above, and its posterior lobe, with the contained posterior cornu and hippocampus minor, more or less rudimentary. Every marmoset, American monkey, Old World monkey, baboon, or man-like ape, on the contrary, has its cerebellum entirely hidden, and possesses a large posterior cornu, with a well-developed hippocampus minor.

"In many of these creatures, such as the Saimiri (Chrysothrix), the cerebral lobes overlap and extend much farther behind the cerebellum in proportion than they do in Man."*

(* Huxley, "Evidence as to Man's place in Nature" page 97.)

It is by no means pretended that these conclusions of British observers as to the affinity in cerebral structure of Man and the Primates are new, but on the contrary that they confirm the inductions previously made by the princ.i.p.al continental teachers of the last and present generations, such as Tiedemann, Cuvier, Serres, Leuret, Wagner, Schroeder van der Kolk, Vrolik, Gratiolet, and others.

At a late meeting of the British a.s.sociation (1862), Professor Owen read a paper "On the brain and limb characters of the Gorilla as contrasted with those of Man"* in which, he observes, that in the gorilla the cerebrum "extends over the cerebellum, not beyond it."

(* Medical Times and Gazette" October 1862 page 373.)

This statement, although slightly at variance with one published the year before (1861) by Professor Huxley, who maintains that it does project beyond, is interesting as correcting the description of the same brain given by Professor Owen in that year, in a lecture to the Royal Inst.i.tution, in which a considerable part of the cerebellum of the gorilla was represented as uncovered.*

(* "Athenaeum" Report of Royal Inst.i.tution Lecture, March 23, 1861, and reference to it by Professor Owen as to Gorilla, ibid. March 30 page 434.)

In the same memoir, it is remarked that in the Maimon Baboon the cerebrum not only covers but "extends backwards even beyond the cerebellum."*

(* For Report of Professor Owen's Cambridge British a.s.sociation paper see "Medical Times" October 11, 1862 page 373.)

This baboon, therefore, possesses a posterior lobe, according to every description yet given of such a lobe, including a new definition of the same lately proposed by Professor Owen. For the posterior lobe was formerly considered to be that part of the cerebrum which covers the cerebellum, whereas Professor Owen defines it as that part which covers the posterior third of the cerebellum, and extends beyond it.

We may, therefore, consider the attempt to distinguish the brain of Man from that of the ape on the ground of newly-discovered cerebral characters, presenting differences in kind, as virtually abandoned by its originator, and if the sub-cla.s.s Archencephala is to be retained, it must depend on differences in degree, as, for example, the vast increase of the brain in Man, as compared with that of the highest ape, "in absolute size, and the still greater superiority in relative size to the bulk and weight of the body."*

(* Owen, ibid. page 373.)

If we ask why this character, though well known to Cuvier and other great anatomists before our time, was not considered by them to ent.i.tle Man, physically considered, to claim a more distinct place in the group called Primates than that of a separate order, or, according to others, a separate genus or family only, we shall find the answer thus concisely stated by Professor Huxley in his new work, before cited:--

"So far as I am aware, no human cranium belonging to an adult man has yet been observed with a less cubical capacity than 62 cubic inches, the smallest cranium observed in any race of men, by Morton, measuring 63 cubic inches; while on the other hand, the most capacious gorilla skull yet measured has a content of not more than 34 1/2 cubic inches. Let us a.s.sume for simplicity's sake, that the lowest man's skull has twice the capacity of the highest gorilla's. No doubt this is a very striking difference, but it loses much of its apparent systematic value, when viewed by the light of certain other equally indubitable facts respecting cranial capacities.

"The first of these is, that the difference in the volume of the cranial cavity of different races of mankind is far greater, absolutely, than that between the lowest man and the highest ape, while, relatively, it is about the same; for the largest human skull measured by Morton contained 114 cubic inches, that is to say, had very nearly double the capacity of the smallest, while its absolute preponderance of over 50 cubic inches is far greater than that by which the lowest adult male human cranium surpa.s.ses the largest of the gorillas (62 minus 34 1/2 = 27 1/2). Secondly, the adult crania of gorillas which have as yet been measured, differ among themselves by nearly one-third, the maximum capacity being 34.5 cubic inches, the minimum 24 cubic inches; and, thirdly, after making all due allowance for difference of size, the cranial capacities of some of the lower apes fall nearly as much relatively below those of the higher apes, as the latter fall below Man."*

(* Huxley, "Evidence as to Man's place in Nature" London 1863 page 78. )

Are we then to conclude that differences in mental power have no intimate connection with the comparative volume of the brain? We cannot draw such an inference, because the highest and most civilised races of Man exceed in the average of their cranial capacity the lowest races, the European brain, for example, being larger than that of the negro, and somewhat more convoluted and less symmetrical, and those apes, on the other hand, which approach nearest to Man in the form and volume of their brain being more intelligent than the Lemurs, or still lower divisions of the mammalia, such as the Rodents and Marsupials, which have smaller brains. But the extraordinary intelligence of the elephant and dog, so far exceeding that of the larger part of the Quadrumana, although their brains are of a type much more remote from the human, may serve to convince us how far we are as yet from understanding the real nature of the dependence of intellectual superiority on cerebral structure.

Professor Rolleston, in reference to this subject, remarks, that "even if it were to be proved that the differences between Man's brain and that of the ape are differences entirely of quant.i.ty, there is no reason, in the nature of things, why so many and such weighty differences in degree should not amount to a difference in kind.

"Differences of degree and differences of kind are, it is true, mutually exclusive terms in the language of the schools; but whether they are so also in the laboratory of Nature, we may very well doubt."*

(* Report of a Lecture delivered at the Royal Inst.i.tution by Professor George Rolleston "On the Brain of Man and Animals"

"Medical Gazette" March 15, 1862 page 262.)

The same physiologist suggests, that as there is considerable plasticity in the human frame, not only in youth and during growth, but even in the adult, we ought not always to take for granted, as some advocates of the development theory seem to do, that each advance in psychical power depends on an improvement in bodily structure, for why may not the soul, or the higher intellectual and moral faculties, play the first instead of the second part in a progressive scheme?

INTELLIGENCE OF THE LOWER ANIMALS COMPARED TO THAT OF MAN.

Ever since the days of Leibnitz, metaphysicians who have attempted to draw a line of demarcation between the intelligence of the lower animals and that of Man, or between instinct and reason, have experienced difficulties a.n.a.logous to those which the modern anatomist encounters when he tries to distinguish the brain of an ape from that of Man by some characters more marked than those of mere size and weight, which vary so much in individuals of the same species, whether simian or human.

Professor Aga.s.siz, after declaring that as yet we scarcely possess the most elementary information requisite for a scientific comparison of the instincts and faculties of animals with those of Man, confesses that he cannot say in what the mental faculties of a child differ from those of a young chimpanzee. He also observes, that "the range of the pa.s.sions of animals is as extensive as that of the human mind, and I am at a loss to perceive a difference of kind between them, however much they may differ in degree and in the manner in which they are expressed. The gradations of the moral faculties among the higher animals and Man are, moreover, so imperceptible, that to deny to the first a certain sense of responsibility and consciousness would certainly be an exaggeration of the difference between animals and Man. There exists, besides, as much individuality within their respective capabilities among animals as among Man, as every sportsman, or every keeper of menageries, or every farmer and shepherd can testify, who has had a large experience with wild, or tamed, or domesticated animals. This argues strongly in favour of the existence in every animal of an immaterial principle, similar to that which, by its excellence and superior endowments, places Man so much above animals. Yet the principle exists unquestionably, and whether it be called soul, reason, or instinct, it presents, in the whole range of organised beings, a series of phenomena closely linked together, and upon it are based not only the higher manifestations of the mind, but the very permanence of the specific differences which characterise every organ. Most of the arguments of philosophy in favour of the immortality of Man apply equally to the permanency of this principle in other living beings."*

(* Contributions to the "Natural History of the United States of North America" volume 1 part 1 pages 60 and 64.)

Professor Huxley, when commenting on a pa.s.sage in Professor Owen's memoir, above cited, argues that there is a unity in psychical as in physical plan among animated beings, and adds, that although he cannot go so far as to say that "the determination of the difference between h.o.m.o and Pithecus is the anatomist's difficulty," yet no impartial judge can doubt that the roots, as it were, of those great faculties which confer on Man his immeasurable superiority above all other animate things are traceable far down into the animate world. The dog, the cat, and the parrot, return love for our love and hatred for our hatred. They are capable of shame and of sorrow, and though they may have no logic nor conscious ratiocination, no one who has watched their ways can doubt that they possess that power of rational cerebration which evolves reasonable acts from the premises furnished by the senses--a process which takes fully as large a share as conscious reason in human activity.*

(* "Natural History Review" Number 1 January 1861 page 68.)

GROUNDS FOR REFERRING MAN TO A DISTINCT KINGDOM OF NATURE.

Few if any of the authors above cited, while they admit so fully the a.n.a.logy which exists between the faculties of Man and the inferior animals, are disposed to underrate the enormous gap which separates Man from the brutes, and if they scarcely allow him to be referable to a distinct order, and much less to a separate sub-cla.s.s, on purely physical grounds, it does not follow that they would object to the reasoning of M. Quatref.a.ges, who says, in his work on the "Unity of the Human Species," that Man must form a kingdom by himself if once we permit his moral and intellectual endowments to have their due weight in cla.s.sification.

As to his organisation, he observes, "We find in the mammalia nearly absolute ident.i.ty of anatomical structure, bone for bone, muscle for muscle, nerve for nerve--similar organs performing like functions. It is not by a vertical position on his feet, the os sublime of Ovid, which he shares with the penguin, nor by his mental faculties, which, though more developed, are fundamentally the same as those of animals, nor by his powers of perception, will, memory, and a certain amount of reason, nor by articulate speech, which he shares with birds and some mammalia, and by which they express ideas comprehended not only by individuals of their own species but often by Man, nor is it by the faculties of the heart, such as love and hatred, which are also shared by quadrupeds and birds, but it is by something completely foreign to the mere animal, and belonging exclusively to Man, that we must establish a separate kingdom for him (page 21). These distinguishing characters," he goes on to say, "are the abstract notion of good and evil, right and wrong, virtue and vice, or the moral faculty, and a belief in a world beyond ours, and in certain mysterious beings, or a Being of a higher nature than ours, whom we ought to fear or revere; in other words, the religious faculty."--page 23.

By these two attributes the moral and the religious, not common to man and the brutes, M. Quatref.a.ges proposes to distinguish the human from the animal kingdom.

But he omits to notice one essential character, which Dr. Sumner, the late Archbishop of Canterbury, brought out in strong relief fifty years ago in his "Records of Creation." "There are writers," he observes, "who have taken an extraordinary pleasure in levelling the broad distinction which separates Man from the Brute Creation. Misled to a false conclusion by the infinite variety of Nature's productions, they have described a chain of existence connecting the vegetable with the animal world, and the different orders of animals one with another, so as to rise by an almost imperceptible gradation from the tribe of Simiae to the lowest of the human race, and from these upwards to the most refined. But if a comparison were to be drawn, it should be taken, not from the upright form, which is by no means confined to mankind, nor even from the vague term reason, which cannot always be accurately separated from instinct, but from that power of progressive and improvable reason, which is Man's peculiar and exclusive endowment."

"It has been sometimes alleged, and may be founded on fact, that there is less difference between the highest brute animal and the lowest savage than between the savage and the most improved Man. But, in order to warrant the pretended a.n.a.logy, it ought to be also true that this lowest savage is no more capable of improvement than the Chimpanzee or Orang-outang."

"Animals," he adds, "are born what they are intended to remain. Nature has bestowed upon them a certain rank, and limited the extent of their capacity by an impa.s.sable decree. Man she has empowered and obliged to become the artificer of his own rank in the scale of beings by the peculiar gift of improvable reason."*

(* "Records of Creation" volume 2 chapter 2 2nd edition 1816.)

We have seen that Professor Aga.s.siz, in his "Essay on Cla.s.sification,"

above cited, speaks of the existence in every animal of "an immaterial principle similar to that which, by its excellence and superior endowments, places man so much above animals;" and he remarks, "that most of the arguments of philosophy in favour of the immortality of Man, apply equally to the permanency of this principle in other living beings."

Although the author has no intention by this remark to impugn the truth of the great doctrine alluded to, it may be well to observe, that if some of the arguments in favour of a future state are applicable in common to Man and the lower animals, they are by no means those which are the weightiest and most relied on. It is no doubt true that, in both, the ident.i.ty of the individual outlasts many changes of form and structure which take place during the pa.s.sage from the infant to the adult state, and from that to old age, and the loss again and again of every particle of matter which had entered previously into the composition of the body during its growth, and the subst.i.tution of new elements in their place, while the individual remains always the same, carries the a.n.a.logy a step farther. But beyond this we cannot push the comparison. We cannot imagine this world to be a place of trial and moral discipline for any of the inferior animals, nor can any of them derive comfort and happiness from faith in a hereafter. To Man alone is given this belief, so consonant to his reason, and so congenial to the religious sentiments implanted by nature in his soul, a doctrine which tends to raise him morally and intellectually in the scale of being, and the fruits of which are, therefore, most opposite in character to those which grow out of error and delusion.