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Show 102 So far as cerebral structure goes, therefore, it is clear that l\tian differs less from the Chimpanzee or the Orang, than these do even from the Monkeys, and that the difference between the brains of the Chimpanzee and of Man is almost insignificant, when compared with that between the Chimpanzee brain and that of a Lemur. It must not be overlooked, however, that there is a very striking difference in absolute mass and weight between the lowest human brain and that of the highest ape -a difference which is all the more remarkable when we recollect that a full grown Gorilla is probably pretty nearly twice as heavy as a Bosjes man, or as many an European woman. It may be doubted whether a healthy human adult brain ever weighed less than thirty-one or -two ounces, or that the heaviest Gorilla brain has exceeded twenty ounces. This is a very noteworthy circumstance, and doubtless will one day help to furnish an explanation of the great gulf which intervenes between the lowest man and the highest ape in intellectual power;* but it has little systematic value, for the * I say help to furnish : for I by no means believe that it was any original difference of cerebral quality, or quantity, which caused that divergence between ibc human and the pithecoid stirpes, which has ended in the present enormous gnlf between them. It is no doubt perfectly true, in a certain sense, that aU difference of function is a result of difference of structure; or, in other words, of difference in the combination of the primary molecular forces of living substance; and, starting from this undeniable axiom, objectors occasionally, and with much seeming plausibility, argue that the vast intellectual chasm botween the Ape and Man implies a corresponding structural chasm in the organs of the intellectual functions ; so that, it is said, the non-discovery of such vast differences proves, not that they arc absent, but that Science is incompetent to detect them. A very little consideration, however, will, I think, show the fallacy of this reasoning. Its validity hangs upon the assumption, that intellectual power depends altogether on the brain-whereas the brain is only one condition out of many on which intellectual manife tations depend ; the others being, chiefly, the organs of the senses and the motor apparatuses, especially those which are concerned in prehension and in the production of articulate speech. A man born dumb, notwithstanding his great cerebral mass and his inheritance of strong intellectual instincts, would be capable of few higher intcllccLua1 manifestations than an Orang or a Chimpanzee, if he were confined to the ~;;ocicty 103 simple :reason that, . as may be concluded from what has been already said respecting cranial capacity, the difference in weight of brain between the highest and the lowest men is far greater, both relatively and absolutely, than that between the lowest man and the highest ape. The latter, as has been seen, is represented by, say twelve, ounces of cerebral substance absolutely, or by 32 : 20 relatively; but as the largest recorded human brain weighed between 65 and 66 ounces, the former difference is represented by more than 33 ounces absolutely, or by 65 : 32 relatively. Regarded systematically the cerebral differences, of man and apes, are not of more than generic value-his Family distinction resting chiefly on his dentition, his pelvis, and his lower li.mbs .. Thus, whatever system of organs be studied, the comparison of their modifications in the ape series leads to one and the same result-that the structural differences which separate Man from the Gorilla and the Chimpanzee are not so great as those which separate the Gorilla from the lower apes. of dumb associates. And yet there might not be the slightest discernible duference between his brain and that of a highly intelligent and cultivated person. The dumbness might be the result of a defective structure of the mouth, or of the tongu:c, or a mere defective innervation of these parts; or it might result from congenital deafness, caused by some minu.te defuct of the internal oar, which only a careful anatomist could discover. The argument, that because there is an immense difference between a Man's intelligence and an A pc's, therefore, there must be an equally immense difference between their brains, appears to me to be about as well based as the reasoning by which one should end-eavour to prove that, because there is a'' great gulf" between a watch that keeps accurate time and another that will not go at all, there is therefore a great structural hiatus between the two watches. A hair in the l>alance-wheel, a little rust on a pinion, a bend in a tooth of the escapement, • a something so slight that only the practised eye of the watchmaker can discover it, may be the source of all the difference. And believing, as I do, with Cuvier, that the possession of articulate speech is the grand distinctive character of man (whether it be absolutely peculiar to him or not), I find it very easy to comprehend, that some equally inconspicuous structural difference may have been the primary cause of the immeasurable and prac• ti.cally infinite divergence of the Human fi·om the Simian Stirps. |