Ewes impregnated by a powerful ram bear more males than females, so long as the ram is in possession of his full forces. After a time the ram has to perform his functions repeatedly during a few days, as great numbers of the ewes are rutting. The fatigued or exhausted ram then begets only females.
Next the number of rutting ewes diminishes. The ram gradually recovers his strength. Whilst constantly employing it with the remaining rutting ewes he again begets male individuals. Now, according to the rule of cross-heredity of sex, the number of females ought to be greatest at the outset, because we here have a male of exceptional force. When the ram is exhausted, according to the theory of cross sexual heredity the males ought to be more numerous. It appears, therefore, that in this experiment of Mayerhofer’s we have something which remains in want of explanation. We shall presently have occasion to speak more fully of the facts which this author communicates respecting the origin of sex in man, and will then return to this subject.
The information which we have concerning a stallion (Sir Hercules) belonging to the stud of Count Lehndorff deserves attention. This stallion was twenty-six years old, and had to cover twenty-three mares. The result was twenty-four foals of the male sex. This case of the ardent mares and the old stallion can be explained by the theory of cross-heredity of sex.
Particular attention should be here directed to a phenomenon which seems to imply that a sexually exhausted individual always has his advantage of propagating his own sex secured. It is a sort of fulfilment of duty on the part of a strong female animal when her litter shows a majority of male individuals, or male individuals only. In this connection may be mentioned the facts communicated by Settegast, Nathusius-Hundisburg, and De la Tellais, who arrived at their results from experiments upon the proportions of the sexes of the offspring of the domesticated mammalia.
Attempts to solve the problem of the origin of difference of sex by means of experiments have been numerous. So early as the last century Platz attempted to carry out experiments with living animals.
The temperaments of the breeding couple ought to be concordant. Both should be either of warm or cool temperament. Warmth and moisture are primary conditions of fertility, not in plants alone, but amongst the animals also; and (as Mayoor Zsigmond, of Kaschau, proclaimed in 1723) represent the primary conditions of the possibility of a conception.
The warm element belongs to the man; the moist to the woman. Where both qualities are to be found in both, offspring may also be anticipated. But if this be not the case, for example, if the man’s warmth does not accord with that of his wife, but is of a higher degree, then he can beget boys. If he be not so warm, he must, if he wishes for sons, make a distinct alteration in his diet. According to the prescription given, he ought to lead a regular life and to limit himself strictly to warm and dry aliments. The temperament of the woman is often ardent and dry. In this state it must be regarded as unfitted for the development of an embryo. Befitting food would not be without an influence upon the alteration of temperament. Respecting this, experiments had proved this much, that a suitable change of diet can exercise a salutary influence over the temperament. A woman who was in the highest degree beautiful in face and in every part comely had a temperament which would accord with that of any man.
Then comes the theory of the allotment of the male and female in man, and in all the vertebrata, to the right and left sides of organs of generation. This is a theory which is being always brought forward, even by the most recent writers, some of whom go so far as actually to wish to support it by experiments.
Thus the excision of one or the other of the testicles of the male is recommended in order that the owner may be able to breed the sex which he desires. It still remains, in order to effect the artificial determination of the sex, that the female should also play her part correctly, so that the semen of the male may be conveyed to an ovule from the required ovary. An effort was accordingly made to secure intercourse in such a manner that the semen of the male might be delivered in a certain direction in agreement with the anatomical position of the duct which was to lead the seed into the required ovary. But it was practically difficult to settle what position in the intercourse was the right one. Experience proved that in a certain case on two successive occasions male individuals were born when the impregnation had been so contrived that the semen should enter the right ovary. Therefore the left ovary was for female offspring. It is not our concern to enter into further explanations of these occurrences. Only this much may be said, that experiments have been constantly made which might lead to some conclusive solution of these questions, without any result having been obtained.