Brain weight

“ Several methods of estimating the sexual proportions of brain mass have been suggested, but only two of them have met with any favor. These are determining the ratio of brain weight to body weight or body height.
According to the investigations of anthropologists of acknowledged authority, the average brain weight of woman is to that of man in England and France as 90 is to 100. The average stature of men and women in the same countries is as 93 to 100. This gives man an excess of brain weight over that of woman of something more than an ounce. ”

“ But, if it must be conceded that the absolute weight of man's brain is greater than woman's, is it likewise true that the relative weight is greater? This is a question which demands an answer, as it is impossible to come to any just conclusion respecting the intellectual capacity of woman expressed in terms of brain weight, unless we can affirm with certainty that men's brains are relatively, as well as absolutely, larger than those of women. ”

“ Brain weight, which is greatest between thirty and forty years, 1,200 to 1,450 grams in man, 1,100 to 1,500 in woman, diminishes toward the sixtieth year. It is said that the diminution takes place a few years sooner in the opposite sex. The estimated loss of weight in a person of eighty years is admitted to be from 90 to 150 grams. Another sign of age is the tendency to degeneration found in the pineal gland, the cortical substance, the optic and striate thalami, and in the brain capillaries.
The state of the eyes, if not too decomposed, may still become a sign of identity. ”

“ The greatest absolute weight is found between twenty-five and thirty-five years of age in the male and a little later in the female. At birth the brain weighs comparatively much more than it does later on, its proportion to the body weight being about 1 to 6. At the tenth year it is about 1 to 14, at the twentieth 1 to 30, and after that about 1 to 36.5. In old age there is a further slight decrease in proportion. In many men of great intellectual eminence the brain weight has been large—Cuvier’s brain weighed 641/2 oz., Goodsir’s 571/2, for instance—but the exceptions are numerous. ”

“ To this list we might have added a large number of persons whose brains weighed less than 53 ounces. Yet the brains of Daniel Webster, Agassiz, Napoleon I, Lord Byron, Baron Dupuytren, General Skoboleff, and other famous men concerning whose large brains much has been said, weighed less than this; and we might have appended hundreds of brain weights of idiots, imbeciles, and other insignificant persons, from 53 ounces down to 49 ounces—probably about the average weight in central Europe. ”

“ It is thought that the relative weight of the brain may be an indication of intellectual endowment, especially when the brain weight is compared with the weight of the rest of the body, and that culture in particular lines increases the surface of the cortex by deepening and multiplying the convolutions. ”

“ There is also apparently no superiority in brain weight in modern over ancient times. The cranial capacity of Europeans between the eleventh and eighteenth centuries, [pg 255] as shown by the cemeteries of Paris, is not appreciably different from that of Frenchmen of today, and the Egyptian mummies show larger cranial capacity than the modern Egyptians. Furthermore, the limits of variation between individuals in the same race are wider than the average difference between races. In a series of 500 white brains, the lowest and highest brains will differ, in fact, as much as 650 grams in weight. ”

“ The reason for a lack of close correlation between brain-weight and mental faculties is not far to seek. The functioning of the brain depends upon the nerve cells and fibres, which do not constitute, by any means, the whole mass of the brain. A brain with many cells and complex connections between the cells may contain less connective tissue than another one of simpler nervous structure. In other words, if there is a close relation between form and ability, it must be looked for rather in the morphological traits of the brain than in its size. ”

“ The whole matter of the relation of intelligence to brain-weight, and of the nature and quantity of energy which is a function of this organ, is, indeed, fundamentally a question of physiological chemistry. The assumption that capacity for muscular work is in direct proportion to the mass is approximately correct; but the assumption that capacity for mental work is in proportion to the mass of nerve substance is a gross error, as anthropologists now very well know. ”

“ It may be inferred from the number of cases pointing to an early attainment of the highest average brain-weight, not that the brain differs from all other internal organs of the human body in attaining its maximum before the period of puberty; but that physical as well as mental vigour are dependent on the maintenance of a nice equilibrium between the brain and the other organs while in process of development. ”

“ Let us add that this organ may, moreover, fall much below this weight without causing cessation of life, or even the absolute disappearance of the intelligence, as in some microcephali. The smallest brains which have ever been weighed are those of Teite, quoted by Wagner, 300 grms. (10·58 oz.) , and that of the woman who formed the subject of a memoir by Gore, 283·75 grms. (10 oz.) . These brains are appreciably inferior in weight to those of the gorilla and orang.
6. In the European White, the maximum weight of a healthy brain perhaps reaches 2231 grms. ”

“ If you reduce it to a mere question of avoirdupois, please be so good as to remember that even greater differences exist among men. For instance, your brain (which is certainly not considered over average) weighs from three to three and a half pounds, while Cuvier's brain weighed over four pounds, giving him the advantage of more than eight ounces over our household oracle! Accidental difference in brain weight proves nothing; for you will not admit your mental inferiority to any man, simply because his head requires a larger hat than yours. ”

“ Several insane persons have had brains of 6412 ounces, 63 ounces, 61 ounces, and 60 ounces, as related by Bucknill, Thurnam, and others. With respect to the brain-weights of the fair sex, anatomical authority asserts that in women with brains weighing 55·25 ounces and 50 ounces, no marked intellectual features were noted. Below 30 ounces, the human brain becomes idiotic in character, so that there appears to exist a minimum weight, below which rational mental action is unknown. The anatomist's conclusions regarding brain capacity and mental endowments are therefore plain. ”

“ Thirty men out of three hundred and seventy-five examined in the West Riding Asylum gave brain weights of 55 ounces and upward, showing that such weights are not so rare as some have supposed. In another asylum in England one out of every dozen brains examined showed a weight of 55 ounces or more. ”

“ We cannot regard this measurement as a constant exponent of intellectual power, as many men with small brains have possessed fine intellects; but as a general feature it certainly is indicative of brain weight, and therefore of relative intelligence. The average human brain weighs 48 ounces, while that of a large gorilla is not over 20 ounces. ”

“ Thus I have pointed out the differences in average brain-weight between different races. Brain-weights are, however, so variable, that a considerable overlapping occurs, and that even the average sizes of the brains of the white race are numerously represented among other races. Medium-sized brains of whites may be represented by the group of individuals having skull 35capacities of from 1450 cc. ”

“ Thus in persons of a height of 175 centimeters, and over, of the male sex, it is found that in a period of from twenty to forty years the brain weight is 1,409 grams. But from forty-one to seventy years it has sunk to 1,363, and in persons of from seventy-one to ninety it has shrunk to 1,330. ”

“ Again, the researches of physiologists of the highest authority seem to have established the fact that the brain acquires its full size and weight at the age of eight years! How can the phrenologist reconcile his philosophy to this stubborn fact? The skull and head continue to grow after the age of eight, but the brain remains the same in weight and size. Everybody knows how the skulls of children change as they grow up, and yet the brains never do. As the child acquires knowledge and develops his mental faculties, the brain remains the same size and weight. ”

“ The discussion on this point has been fully entered into by distinguished anatomists, and need not be detailed in this place. Alone, the weight offers a difference. The heaviest human brain known is given at 1,872 grammes, the lightest brain of a sane person 907 grammes, both these extremes being furnished by women. ”

“ The weight of the average female brain has been estimated at from five to six ounces less than that of the average male brain, and a general inferiority in size exists at every period of life, from the new-born infant to old age. ”

“ There are some observations which support the conclusion that the brain attains its greatest weight before 30 years of age, and then undergoes diminution. At the age of 80 this diminution is supposed to reach 10 per cent. ”