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Page:Popular Science Monthly Volume 54.djvu/261

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BRAIN WEIGHTS AND INTELLECTUAL CAPACITY.

the same as that of the skull of Joachim, an imbecile six feet nine inches in height, with a brain weight of 61.2 ounces, whereas Spurzheim's brain weighed only 55 ounces.

Whoever has examined heads in the dissecting room of a medical college knows that, except in rare cases of disease, the brain does not fit the skull, but is surrounded by three membranes and a watery fluid; and this liquid, it has been ascertained, is generally sufficient to admit of its performing certain movements.

There can be no doubt that the brain moves in the skull, changing its position, according to the laws of gravitation, in much the same way as the lungs, heart, and liver do in the body. It has been observed many times to move, as well as to pulsate, when exposed to view during the life of the individual. It is subject to two regular and constant motions—one produced by the arteries, the other by respiration. It has also a third motion, discovered and described by Dr. M. Luys, who stated, in a paper read before the Academy of Medicine of Paris, that "the brain is subject to certain changes of position, dependent on the attitude of the body. Thus, if a man lies on his back or side, or stands on his head, the brain undergoes certain changes of position in obedience to the laws of gravity; the movements take place slowly, and the brain is five or six minutes in returning to its previous position." From these anatomical data M. Luys deduced some interesting and practical conclusions, by which he explained, for example, the symptoms of vertigo which feeble persons experience when suddenly rising from a horizontal position. He suggested whether the pains of meningitis may not be due to an interference with these normal movements, and urges the value of giving the brain the change produced by a horizontal position at night.

The average cranial capacity is admitted to be 96 cubic inches in England and 94 in New York; and it is to the unusual quantity of fluid of some cases, and to the extraordinary thickness of the skull in others, that we are to attribute the frequent discrepancy between the external dimensions and the size of the encephalon. Daniel Webster's cranial capacity was 122 cubic inches, yet his brain of 53.5 ounces was just what George Combe has laid down as the average weight for an adult man. Water and lymph, we are told, filled the skull. Professor De Morgan's head, almost free from hair, measured 24.87 inches in circumference, and the dimensions were all those of a very large head, sufficient to contain from 65 to to ounces of brain, yet his brain weighed only 52.75 ounces, or little, if at all, above the average in the cold parts of the temperate zones. De Morgan was sixty-five years of age when he died. He was much emaciated, and "the brain was distinctly