288 THE POPULAR SCIENCE MONTHLY. 



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 f mental action, we shall give his estimate of the cere- 

 brum, or "brain," as "ministering, so far as any material instrument 

 may do, to the exercise of these psychical powers which, in man, ex- 

 hibit 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-cen 

 tres. 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 undulatorj' 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 tlie other anatomically, must differ widely in function, 

 notwithstanding their similarity of location and structure. When we 

 take into consideration that the forces of oi-ganic 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 im- 

 possible 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. 



