I adduce this instance, for the sake of remarking respecting it, that on this subject also controversies exist, which must be settled by wider studies of the life of plants.
Cornaz has tried to derive from cows evidence in support of Thury’s theory. He had twenty-nine cows impregnated with attention to the rutting time, and from twenty-nine births received twenty-two females and seven males. Cornaz attested his experiment by a declaration, and the experiment was repeated in the French state domains.
But the experiment alone was striking enough to invite repetition. It also met with partial success. But the plan was afterwards entirely given up, perhaps in consequence of disappointments.
In this case it very likely happened—as in such experiments it very easily may happen—that, in consequence of insufficient practical knowledge on the part of the experimenter, the actual commencement of the rutting time was overlooked. In addition, it is well known that animals, in consequence even of an amount of exercise not very exhausting, and in many other ways, as well as in consequence of the food they have taken, may exhibit variations in the activity of their rutting. It is not, therefore, surprising if the results of experiments show much that was unexpected.
I here pass over a great number of proofs which Thury gives in his essay. Funcke (1866) made in his ‘Physiology’ the following remarks on Thury’s theory:—“Although the origin and determination of sex is not indisputably proved to depend upon the degree of ripeness of the ovum, it appears to me that we have not reached the right time for determining the factor upon which it does depend. These experiments have been made to repose upon a fact, which fact certainly proves, beyond the possibility of dispute, a relation between the fertilization of the ovum and the subsequent sex. This fact is that, in the case of certain creatures capable of parthenogenesis (unisexual procreation), we find that, from unfertilized ova one sex always results, and from fertilized ova the other. But any closer interpretation of this function of the semen is rendered nugatory in advance by this, that it is in some cases the male and in others the female that results from the unfertilized ova.”
Thury’s theory can be very suitably brought into agreement with the theory of cross-heredity of sex, and explained by the assistance of that view. The cow, at the beginning of her rutting, is not in a condition of great sexual vigor. If the ovum be effectually fertilized, it may be supposed that the bull, in procreative activity the superior consort, will be fitted not to reproduce his own sex, but that of the weaker cow. At the end of the rutting period the cow, which is brought to the bull, has her ovum ripened to the highest possible degree, and in consequence, when compared, from a sexual point of view, with the bull, is distinctly the stronger and superior, and a male calf is in this case the result of conception.
According to the theory of cross-heredity of sex, female creatures should in the former instance be produced, and in the latter males, which same result is reached in accordance with the theory of Thury.
Attempts have been also made to apply Thury’s theory to the human species. The menstruation of women has been compared with the rutting of the lower animals, and has been considered a protracted, oft-repeated rutting. Now, as an ovum is specially developed every month, it follows that this ovum requires a certain part of a month to attain a more or less advanced degree of ripeness. According to this, the ova which are fertilized a short time after menstruation will develop only female individuals, whilst those which have had a longer time in which to attain to ripeness would develop themselves into males.
The mucous membrane of the womb ought, about ten days before the beginning of menstruation, to thicken itself distinctly in consequence of a turgescence and dilatation of the vessels. In consequence it appears swollen and loosened, and it has reached the culminating point of swelling when the menstruation is at its highest. After menstruation the swelling does not immediately decrease, but lasts on for about nine days, until the mucous membrane returns to its normal condition. (Hensen.) Thus it seems that the swelling and hyperæmia in the womb appear at the same time as the conditions which lead to the ripening of the ovum. The fertilization of the human ovum would be, therefore, most efficacious at the time when the mucous membrane of the womb is also most appropriately prepared, and it is probable that the same moment is the one when all the other coincident factors are of a sort best calculated for the reception, the fixing, and the protection of the ovum. It is simultaneously with these processes in the mucous membrane of the womb, and in the other parts of the generative organs of the woman, that the ripening of the ovum is effected.