Serious surgical interference with the female certainly has an effect upon fecundation. At least, pregnancy appears to be postponed after the more difficult operations. If, however, impregnation takes place, either male or female offspring may be anticipated. This contradicts the theory of cross-heredity of sex, according to which only individuals of one sex should appear, if one ovary has been removed. Facts which have been brought to light by experiments with animals, and by observation in the human subject, tend to give the theory of cross-heredity of sex a higher value. But under the same circumstances, other phenomena present themselves to observation which appear to render some of the postulates of this theory untenable. Various diseases which are diagnosed by medical men as organic disorders, but which do not interfere with the power of reproduction, are apparently without influence on the sex of the offspring, and also without influence upon a striking prevalence of one or the other sex. Richarz assigns all the power to the fecundated female individual. He thus raises the culminating point of the female power of reproduction to a height above that which other specialists will allow. In this he is in complete disagreement with Roth, to whom he is also opposed in other directions. Within certain individual limits (amongst which is not to be included a diminution of capacity in consequence of the necessary periodical functional impulses), the female organism discharges its functions the more frequently and the more perfectly the less often it is called into operation, and, _e contra_, the less frequently and the less perfectly the more often it is called into operation. According to Vernich, very long intervals between successive pregnancies disturb the progressive increase in the weight of the children less than very short ones. One may, without being afraid of making any great mistake, at any rate in the case of women who bear many children, make the same assertion respecting the constantly increasing probability of male offspring, as respecting the increase of weight. The beneficial effect of a fairly long fallow season upon these periodically acting organs is revealed in this way among others, that, often enough, in consequence of prolonged rest and recovery of strength, the female generative organs, after frequent still births, became capable of producing healthy children. (Richarz.) The fundamental law of crossing is supported by this author in every direction. He recommends it as revivifying the blood and tissues, in order to combat the evil effects of inbreeding, the exhaustion of normal and healthy conditions, and as a preventative against the appearance of degeneration and decay. A similar relation between the sexes exists in their functions for the continuation of the species.