son from product to structure until after we have internal evidence of the functional relations between the structure and product of the class of organs to which those under test belong; nor can we without such knowledge even reason to the general quality of two organs by their different product, unless our comparisons are made under the same environment. For instance, take two pairs of lungs: let one respire at sea-level, the other at the top of Mont Blanc. Their absolute product would be no estimate of their relative capacity. Still, the physiologist would have little difficulty in eliminating the effect of difference of circumstances in his calculation, because his complete knowledge of the lungs and of the influence of atmospheric pressure enables him to allow for differences of environment. But no such allowance can be made in estimating the normal power of the male and female brain which have always acted in different mental atmospheres; for the relation of structure to function as regards brain has not been accurately determined.
It is because of this lack of knowledge regarding the precise connection between brain-structure and thought, and not because of imperfection in the data of measurements, that students refuse to draw therefrom the law of brain capacity; and thinkers will not infer the capacity of male and female brains from their products, until the different influences acting upon men and women can be eliminated. While anatomy is unable to solve for us the enigma of sexual brain-power, we may have recourse to comparison under similar environment as the key to our problem. This method of discovery Miss Hardaker, with a perversity remarkable in a disciple of modern science, is laboring zealously to prevent.
"We need not," she says, "ascertain the meaning of brain-size by experiment; we can arrive at it by analogy. All other organs (under the same conditions) work in proportion to their size. Is there any good reason for making an exception of the brain?" (page 578). Now, even if all other organs work in proportion to their size, the fact that the brain is exceptional, in the nature and in the variety and complexity of its functions, would render the argument from biceps to brain as questionable as that from marble to zinc. There may be properties in common, but in the production of forces the similar effects of these common properties may be wholly vitiated by others peculiar to only one of the objects compared. Besides, size is not always a gauge of organic capacity. Does the large eye see better, the large ear hear more, the large nerve feel more keenly? And, if, all other conditions being equal, they might do so, the incalculable variation of condition renders the size test of no practical value at all. This, however, is a phase of the subject to be discussed later, when we shall endeavor to show that, although we agree with Miss Hardaker that a larger brain means something, it does not necessarily mean a "greater amount of thinking in a given time." And, here we throw in, as interesting