excluding the pituitary body and pineal gland, weighed, immediately after its removal from the cranium, exactly 15 oz. Deducting the weight of the membranes afterwards removed (about 12 oz.) and allowing for the blood which these would contain, as well as for the short piece of the spinal cord attached to the medulla, I calculated that the nervous mass of the encephalon, in the quite recent state, weighed at least 14 oz. This is an absolute weight, greater than that of the brain of the young orang, described by Dr. Rolleston in the last number of this Journal (p. 207), which weighed only 12 oz. It also surpasses the absolute weights (934 oz. and 1314 oz.) of the brains of a half grown male and of a female Chimpanzee, as given on the authority of Professor Owen.[1] The brain of this young animal is, so far as I am aware, the heaviest Simian brain yet on record. It is, however, light indeed, in comparison with the weight of the human brain in a child at about a corresponding period of dentition, which would average at least 38 oz.[2]
The ratio between the weight of the entire brain (14 oz.) and the body (264 oz.) in our Chimpanzee, both taken in the recent state, and without any sign of emaciation in the animal, is very nearly as 1 to 19, so that the brain was relatively heavier than in Dr. Rolleston's young orang, in which the ratio was as 1 to 22⋅3. Fitting such a brain to the body of the nearly adult female Chimpanzee, stated by Prof. Owen,[3] to weigh 976 oz., the proportion would be as 1 to 70. The actual proportions observed in the female Chimpanzee mentioned above, whose body weighed 680 oz., were 1 to 51. But much as this, unusually heavy, young Simian brain raises previous estimated ratios, it still remains far below the human proportion, taken at a corresponding age. In Huschke's case of the child of six years, the ratio was 1 to 11; and the proportion in the human adult, is usually given as 1 to 36, or as 1 to 40, in cases of persons killed or dying suddenly, whilst the body is in a healthy state.[3] This, however, refers to European brains. In regard to other races our information is defective.
At the end of several months, the entire brain of our Chimpanzee, hardened and shrunk from the action of the spirit on its watery, saline, and fatty ingredients, weighed only 9 oz. and a few grains. In dissecting its right half, care was taken to weigh the fragments of the cerebral hemisphere, and to ascertain the weight of the right half of the cerebellum, and that of the pons, with the medulla. The weight of the left half of the brain, which still remained undissected, was also recorded. With these elements, and assuming that every part of the brain had equally lost weight from the action of the spirit upon it, it was easy to estimate approximately the separate weights of the cerebrum, cerebellum, and pons, with the medulla, in
