the known to the unknown. These fixed points are to be found in anatomy and physiology. We may also study certain voluntary acts of the sexes in the aggregate, and estimate the difference in the result. The relations between the sexes will also furnish facts from which mental differences may be estimated.
Accepting Dr. Carpenter as the exponent of thought upon the physiology of mental action, we shall give his estimate of the cerebrum, or "brain," as "ministering, so far as any material instrument may do, to the exercise of these psychical powers which, in man, exhibit so remarkable a predominance over the mere animal instincts." The brain, anatomically, may be classed, among the ganglia, having its function more clearly defined than is usual with great nerve-centres. It is not an assumption, then, which will provoke dissent among modern physiologists, to assume the brain as the "organ of thought;" not in the sense that it secretes thought, but that it presides in its own way over its special function, that of intellection. It is the operation of the brain in its functional capacity which gives to each individual his mental peculiarities. These differences in mental action which define the individual must represent differences in functional activity. Taking this view of the physiology of thought, it is just to say that this exhibit of mental differences is the measure of functional, if not of structural, peculiarities, in the great brain-ganglion. If this is true of several individuals, it must also be true of the sexes. The mental traits, which define the sexes intellectually, afford a measure of either functional or structural differences in the cerebral ganglion. It is very possible that, histologically, any structural differences which may exist in the ganglia of either individuals or the sexes may never be determined. But the drift of modern thought and research tends to show that such differences do exist, and it is as true approximately as the undulatory theory of light. Many of the functional attributes of sex are presided over by ganglia having special reference to these functions, and these groups of nerve-centres in the sexes, one being the analogue of the other anatomically, must differ widely in function, notwithstanding their similarity of location and structure. When we take into consideration that the forces of organic and functional life represent simply the sum of ganglionic activity, a just idea may be formed of the extent to which this activity must be differentiated in the sexes. It is simply necessary to extend the field of ganglionic action to the brain, the supreme ganglion of all, in order to realize the fact that here also functional differences must exist. That the brain possesses functions in common to the sexes in no wise renders it impossible to perform its part as an organ embraced in the sexual cycle. The relations existing between the sexes are mutually voluntary, and involve more or less of mental action. As these relations represent the opposite poles of structural and functional life, this mutuality must also represent phases of mental action which exist as sexual traits.
