Science has of late years advanced far in this matter, yet it has not much more than begun. There is, as yet, no approximation to unanimity of decision, though the way has been cleared of many errors. This is all that has really been done by the ablest observers, who seem, however, unwilling, if one may say so without presumption, to accept the conclusions to which their own experiments and observations would seem to point. Take an illustration. The early certitude on the sex-differences in the weight of the brain and in the proportion of the cerebral lobes has been completely turned upside down. The long believed opinion of the inferiority of the woman in this direction has been proved to be founded on prejudice, fallacies, and over-hasty generalisations, so that now it is allowed that the sexual differences in the brain are at most very small. An even more instructive example arises from the ancient theory that there was a natural difference in the respiratory movements of the sexes. Hutchinson even argued that this costal breathing was an adaptation to the child-bearing function in woman. Further investigations, however, with a wider basis and more accurate methods--and one may surely add more common-sense--have changed the whole aspect of the matter. This difference has been proved to be due, not to Nature at all, but wholly to the effect of corset-wearing and woman's conventional dress. There is, it would seem, no limit to the quagmire of superstition and error into which sex-difference have drawn even the most careful inquirers if once they fail to cut themselves adrift from that superficial view of Nature's scheme, by which the woman is considered as being handicapped in every direction by her maternal function. Enough has now been said to indicate the complication of the facts, to say nothing of their practical application. I must refer my readers for further details to convenient summaries of the sexual differences, in Havelock Ellis's _Man and Woman_; Geddes and Thomson's _Sex and Evolution_; Thomas's _Sex and Society_; and H. Campbell's _Differences in the Nervous Organisation of Men and Women_: the first of these is a treasure store of facts, and may be regarded as the foundation of all later research; the last is, perhaps, the most generally interesting, certainly it is the most favourable in its estimate of women. Dr. Campbell urges with much force the fallacy of many popular views. He does not seem to believe in the fundamental origin of maleness and femaleness, holding them rather to be secondary and derived, the result, in fact, of selection.