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How much does the human brain weigh?

The average weight of the adult male brain is 49 ounces; that of the adult female, 44 ounces. Although the brains of men weigh more than those of women, the relative weights of the brain and body of the two sexes are about the same. Women, it appears, have slightly heavier brains than men in proportion to the size of their bodies. Taller and heavier persons generally have correspondingly heavier brains. As a rule in the animal kingdom the larger the brain the higher the animal is in the evolutionary scale, and the brain of man is heavier than that of any animal in proportion to the size of the body. The human brain, a development of the upper end of the spinal column, is probably the most highly developed and complex structure in the world. It contains from nine to fifteen billion nerve cells and neurons and the number is no greater in a large brain than in a small one. The brain cells used in a single mental effort, it is estimated, weigh only one-fourth of an ounce, or .01 percent of the body weight. The "gray matter" represents 38 percent of the total weight of the brain. At birth the brain is one-third of its ultimate size and comprises about one-eighth of the child's weight. During the first year the weight of the brain increases 200 to 300 percent. At the age of six it reaches almost its full size. Most authorities believe it ceases to grow entirely at about sixteen or eighteen except in unusual cases, although others think it may grow slightly until middle life. At about sixty the brain begins [page 86] to shrink somewhat and at eighty it generally has lost about 6 percent of its weight. Experts on brain anatomy disagree upon the relation­ship between size and quality in brains. Apparently the weight is not a true index to the mentality of the individual. Aleš Hrdlička found that 150 scientists had bigger and broader skulls, indicating larger brains, than the average person in America. He believed that skulls of "brainy persons" are thinner than those of the average and that their brains continue to grow slightly as long as they are used actively. The brains of living persons cannot be weighed and the weight after death may be considerably less than it was previously. Daniel Webster's brain weighed 53½ ounces, but, judging from the large external measurement, the doctor who made the autopsy in­ferred that Webster's brain may have weighed as much as 66 ounces in its presenile condition. One of the heaviest brains that has been weighed was that of the Russian novelist Ivan Sergyeevich Turgenev. It weighed 74 ounces. The brain of the French naturalist Cuvier weighed 64 ounces, that of Leon Trotsky 56 ounces, and that of Wil­liam Makepeace Thackeray, notable for his massive head, 58 ounces. On the other hand, the brain of Gambetta weighed only 39 ounces and that of Anatole France 35 ounces, considerably less than those of average men of comparable stature. There are records of an insane person whose brain weighed 60 ounces and of two epileptics whose brains weighed 62 and 64 ounces respectively. Pia mater is the name of the delicate cord and tissue connecting the brain and spinal cord. Literally it means "tender mother," being derived from Latin pia, feminine of pius, "tender" or "kind", and mater, "mother."