Page:Popular Science Monthly Volume 20.djvu/596

578 the female than the negro the negress. The difference in the average capacity of the skulls of male and female among modern Parisians is almost double that between the skulls of the male and female inhabitants of ancient Egypt. . . . The general superiority, in absolute weight, of the male over the female brain exists at every period of development. In. new-born infants, the brain was found by Tiedemann to weigh from 14 ounces to 15 ounces in the male, and from 10 ounces to 13 ounces in the female. The maximum weight of the adult male brain, in a series of 278 cases, was 65 ounces; the minimum weight, 34 ounces. The maximum weight of the adult female brain, in a series of 191 cases, was 56 ounces; the minimum, 31 ounces. In a large proportion the male brain ranges between 46 and 53 ounces, and the female between 41 and 47 ounces. A mean average weight of 49 ounces may be deduced for the male, and of 44 ounces for the female brain." It is further given, on the authority of Gratiolet and others, that the male brain can not fall below 37 ounces without involving idiocy; while the female may fall to 32 ounces without such a result. AH accepted authorities agree that the average male brain exceeds the average female brain in weight by about ten per cent. Professor Thurnam also adds, "The brain-weight of the male negro is the same as that of the female European."

Of qualitative differences of brain we know next to nothing; we can not study quality from the physiological side, but are driven to an appeal to the concrete products of brain activity. Yet it is most probable that we may at some time establish an exact correspondence between brain-substance and intelligence, as the size and condition of the lungs yield an exact measure of the breathing power, and as the contractile muscle of the heart measures the quantity of blood ejected at each pulsation. In the case of every other organ of the body we know that there is an ascertainable correspondence between size and condition, and the amount of work which the organ can do. Is there any good reason for making an exception of the brain? The plethysmograph (described in "The Popular Science Monthly" for July, 1880) measures the amount of blood sent to the brain in any particular process of thought, and records the exact time for each process. We shall, doubtless, some time find it to be as complete a physical impossibility for a small and simply organized brain to do a great amount of thinking within a given time as for a small heart to eject a large quantity of blood at each beat, or for small lungs to absorb large amounts of oxygen at each inspiration. Now, if we are not yet certain of the kind and degree of structural differences in the brains of men and women, we still have overwhelming external evidence of the existence of such differences. We have as much external evidence of the superior quality of the masculine brain as of the superior breathing power of the masculine lungs, or of the superior absorbing power of the masculine stomach. We do not examine a muscle to