- Chimpanzee,38 : 101 mm. = 1 : 2⋅66.
- Orang,35 : 96= 1 : 2⋅74.
- Human child,22 : 96= 1 : 4.36.
- Adult man,50 : 157= 1 : 3⋅1.
Hence, it is clear 1°, that the cerebellum in the Chimpanzee and in the Orang are proportionally larger than in man; 2°, that the Orang in this respect approaches man more closely than does the Chimpanzee."—"Anatomical Investigation," &c., l. c. pp. 265–7.
The authors go on to remark that the same large proportion of the cerebellum to the cerebrum is characteristic of the lower Mammalia, as Soemmering had already observed, and that, consequently, the uncoveredness of the cerebellum arises as much from the disproportionately large size of the latter, as from the defect of the posterior lobe of the cerebrum. They further show that the human cerebellum is proportionally still smaller in a six-months' fœtus (1 : 4⋅7); and that, while in the adult the cerebellum has more than double the size it had in the new-born child (50 : 22), the cerebrum of the adult is only 112 times as large in the adult as in the new-born child (157 : 96). At the same time the cerebellum attains its full size by the end of the third year—a fact which indicates very interestingly the relations of the cerebellum with the locomotive power.
M. Gratiolet commences his description of the cerebral convolutions of man thus:—
"The form of the human brain is well known. Its singular height, the width of the frontal lobe, whose anterior extremity, instead of narrowing to an acute point, is terminated by a surface whose extent corresponds to that of the frontal bone; the large angle which the two orbital fossæ form, the depression of the fissure of Sylvius, the richness and complications of the secondary convolutions, at once distinguish this brain from that of all the Primates. But these differences, great and characteristic as they may be, yet consist with the existence of such analogies between the brain of man and that of apes, that the same general description serves both equally well. There are the same principal divisions, the same lobes, the same convolutions; all the parts are not the same, but they are homologous."—L. c, pp. 57, 58.
M. Gratiolet then goes on to point out what the differences of these homologous parts are; but I cannot give them in detail here, without entering upon a full explanation of his terminology, which would occupy too much space.
There is no lack, then, of real differences enough between the brain of man and those of the highest Quadrumana, though they are not those which have been asserted to exist. The question, what is the value of these differences? could only be satisfactorily answered, if the extent of variation exhibited by the brain among the different races of mankind had been carefully determined. We are greatly in want of knowledge on this important subject; but what little is known tends distinctly to the conviction, that no very great value can be set upon these distinctions, inasmuch as the differences between the brains of the highest races and those of the lowest, though less in degree, are of the same order as those which separate the human from the simian brain. I am
