Page:Natural History Review (1861).djvu/310

298 the recent state. The weights of these three portions of the hardened encephalon, respectively, were 7⋅5 oz. avoirdupois, 1⋅3 oz. and ⋅2 oz.; so that the recent cerebrum would have weighed 11⋅66 oz., the cere- bellum 2⋅02 oz., and the pons and medulla ⋅31 oz.

According to these calculations, the cerebrum in the young Chimpanzee is to the cerebellum, as 5⋅75 to 1 nearly. In the adult man it was found by Dr. John Reid to be about 8⋅5 to 1; and in the new born child it appears from Huschke and others, to be at least 13 to 1. In a child five years of age the ratio would probably be somewhere between these. By the test of weight then, which I am not aware to have been applied before, to the separate parts of the Simian brain, the cerebrum of the Chimpanzee is found to be much smaller, in proportion to its cerebellum, than is the case in man.

To carry still further this mode of comparison, we may next contrast the relative weights of the cerebrum and body, and then of the cerebellum and body, in man and the Chimpanzee, by which double contrast, we see, at once, the relative superiority in size of the cerebrum, in man, and of the cerebellum, in the ape. Assuming the ratio of 1 to 40, between the brain and the body in an adult healthy man, and of 8⋅5 to 1, between his cerebrum and cerebellum, then the proportion between his cerebrum and his body will be 1 to 44⋅7 and between his cerebellum and his body 1 to 380; whilst in our Chimpanzee, the proportions as estimated above would be 1 to 22⋅6, and 1 to 131. It is desirable that many more observations on the weights of these separate parts of the encephalon in the several races of men, and in animals, as compared with their bodies, should be collected: they would yield neater results than those arising from measurements, for reasons which will presently be abundantly illustrated.

General form, dimensions, and relative position of the parts of the Encephalon. Notwithstanding the care with which the Chimpanzee's brain had been placed, with its upper surface resting on a bed of cotton wool, in the spirit in which it had been preserved, a marked distortion of its shape had taken place, by the time it was perfectly hardened. Such a deformation must occur, to a greater or less extent, in every brain removed from its cranial case, and placed in a similar position. Its effects are surprising to those who are not familiar with them, and cannot be correctly estimated, without comparing the so altered brain with a cast of the interior of the cranial cavity, from which this soft, pulpy, organ has been extracted. It influences the form of the encephalic mass in all three of its cubical dimensions. The general results are, a slight lateral bulging of the cerebral hemispheres, opposite the parts tied together by the corpus callosum; a more marked falling asunder of the hemispheres at each extremity, but especially behind; a moderate elongation of the hemispheres; and lastly, a very marked, compensating flattening, on both the upper and under surfaces, but especially, on the former, so that its characteristic convexity is completely lost. Moreover, the cerebellum, together with the pons and medulla, drag on the cerebral peduncles, so as to make these latter