But (it is said) there is anatomical evidence of the superior mental capacity of men compared with women: they have a larger brain. I reply, that in the first place the fact itself is doubtful. It is by no means established that the brain of a woman is smaller than that of a man. If it is inferred merely because a woman's bodily frame generally is of less dimensions than a man's, this criterion would lead to strange consequences. A tall and large-boned man must on this showing be wonderfully superior in intelligence to a small man, and an elephant or a whale must prodigiously excel mankind. The size of the brain in human beings, anatomists say, varies much less than the size of the body, or even of the head, and the one cannot be at all inferred from the other. It is certain that some women have as large a brain as any man. It is within my knowledge that a man who had weighed many human brains, said that the heaviest he knew of, heavier even than Cuvier's (the heaviest previously recorded,) was that of a woman. Next, I must observe that the precise relation which exists between the brain and the intellectual powers is not yet well understood, but is a subject of great dispute. That there is a very close relation we cannot doubt. The brain is certainly the material organ of thought and feeling: and (making abstraction of the great unsettled controversy respecting the appropriation of different parts of the brain to different mental faculties) I admit that it would be an anomaly, and an exception to all we know of the general laws of life and organization, if the size of the organ were wholly indifferent to the function; if no accession of power were derived from the greater magnitude of the instrument. But the exception and the anomaly would be fully as great if the organ exercised influence by its magnitude _only_. In all the more delicate operations of nature--of which those of the animated creation are the most delicate, and those of the nervous system by far the most delicate of these--differences in the effect depend as much on differences of quality in the physical agents, as on their quantity: and if the quality of an instrument is to be tested by the nicety and delicacy of the work it can do, the indications point to a greater average fineness of quality in the brain and nervous system of women than of men. Dismissing abstract difference of quality, a thing difficult to verify, the efficiency of an organ is known to depend not solely on its size but on its activity: and of this we have an approximate measure in the energy with which the blood circulates through it, both the stimulus and the reparative force being mainly dependent on the circulation. It would not be surprising--it is indeed an hypothesis which accords well with the differences actually observed between the mental operations of the two sexes--if men on the average should have the advantage in the size of the brain, and women in activity of cerebral circulation.