Page:Popular Science Monthly Volume 26.djvu/25

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15
MIND AND THE NERVOUS SYSTEM.

an intellect which is described as infantine. She could say a few words, such as "good," "child," "morning," with tolerable distinctness, but without connection or clear meaning, and was quite incapable of anything like conversation. Her habits were decent and cleanly, but she could not feed herself—at least with any degree of method or precision. She was fond of carrying and nursing a doll. In a case described in a subsequent number of the same journal, by Professor Marshall, the weight of the entire brain was but 812 ounces. The subject was a boy twelve years of age. Nothing is said relative to the intelligence manifested.

Absolutely, the normal human brain is larger than that of any other animal, except that of the elephant and the whale. Relatively to the height of the body, it very greatly exceeds the proportion existing in either. Leuret found the mean proportional weight of the brain to the rest of the body to be in fishes as 1 to 5,668. The range in these animals is, however, very great. In the bass, I found it, as the result of eleven observations, to be as 1 to 523; in the eel, twenty-two observations, as 1 to 1,429; and in the garfish, nine observations, as 1 to 8,915.

In reptiles of different orders Leuret determined the average to be as 1 to 1,321. I found the proportion in frogs to be as 1 to 520; in lizards, as 1 to 180; and, in the rattlesnake, as 1 to 1,825. The brain of an alligator, over six feet in length, which I examined, weighed but a little over half an ounce.

Next in order come the birds, and here we find a very decided increase in the proportion. From many determinations made by Haller, Cuvier, Cams, and himself, Leuret gives the average as 1 to 212. In the tomtit he found it as 1 to 12; in the canary-bird, as 1 to 14; in the pigeon, as 1 to 91; in the duck, as 1 to 241; in the chicken, as 1 to 377; and, in the goose, as 1 to 3,600. These are very great differences, and, as Leuret remarks, have no constant relation to the intelligence. It is worthy of notice that the brain is proportionally smaller in those birds which are domesticated, and which, consequently, do not have to make so severe a struggle for existence, than in the wild birds; and their brains, therefore, are more encumbered by fat. From determinations that I made, it was ascertained that the brain of the canary-bird reared in the United States was in weight compared to that of the body as 1 to 10·5, and in the Arctic sparrow as 1 to 11. No observations on record show proportionally larger brains than these.

Among mammals we find a still greater increase in the weight of the brain as compared with that of the body. Leuret found it to range in the monkeys from as 1 to 22, 24, and 25; in the dolphin it was as 1 to 36; in the cat, as 1 to 94; in the rat, as 1 to 130; in the fox, as 1 to 205; in the dog, as 1 to 305; in the sheep, as 1 to 351; in the horse, as 1 to 700; and, in the ox, as 1 to 750. The mean for