De Bay, who was opposed to the theory of the anteriorly-developed sexual products of the right and left ovaries, asserts that the quality of the generative products depends upon the quantity of nitrogen existing in the chemical composition of the ovum and the semen. A large proportion of nitrogen in the ovum occasions the development of a girl. If, on the contrary, the semen contains a great quantity of nitrogen, a male individual will result. To determine the proportion of nitrogen, or to give it scientific value in such cases, seems to be a difficult matter.
Mention is also made of cases of tubal pregnancy in which the sex was determined, and an effort has been made here, also, to find some support for the theory of the existence of sex in the ovum whilst in the ovary on the right or left side. Fourteen of these tubal pregnancies, described by different authors, showed boys on the right and girls on the left side. (Seligson.) In such anomalous cases where the embryo has developed itself in the Fallopian tube, and has not reached the uterine cavity, there is no doubt that the developed ovum originated in the ovary of the side on which it was found.
Efforts are made to confute the different objections raised in many quarters. The mention made by the traveler, Peter Kolben, of the practice of cutting out one testicle, which is the custom of certain African tribes (this is contradicted by Le Vaillant [1784], and by Fritsch [1880]), and the accounts of Otto Finsch, may not deserve credit, as they rest upon assertions made by other persons. Accounts are further given, drawn from medical experience, of men who, after prolonged orchitis, with consequent occlusion of the vas deferens, begot only children of one sex, or in other cases were unable to induce pregnancy. Also the discharge of semen was asserted not to take place from both spermatic ducts at the same time. After many digressions, Seligson in the end adheres to Hencke’s theory on no sufficient grounds, and then bases on that theory a method, upon which I shall not here pass judgment, but merely mention it without describing it.
At all events, there can be no question of a compression of the spermatic cord in any way, for it could not be accomplished, either manually or with the aid of various kinds of apparatus, without giving rise to excessive pain.
In this case, as Hencke in his time explained, the cremaster muscle raises the testicle up towards the inguinal canal. At complete erection the testicle is drawn up and pressed against the inguinal ring. This gives more favorable conditions for leading the semen forward from this one of the two testicles; and this portion of the semen is used for impregnation, to which end also a favorable attitude and a free passage into the ovary must be provided. According to the views of the author, this method, if adopted in procreation, will lead to the desired result of producing a given sex. Exceptions are admitted. Exceptions occurred in five families with twenty-three children. The author clings firmly to his theory that each testicle possesses its own special spermatozoa and each ovary its special ova, in which a given sex is already in existence, and from which in fruitful intercourse male or female individuals originate.
Next after a number of theories which have been current on this subject, we reach some others, to which more or less value has been attributed. Morello attached weight to the concentration of the semen. Thin, liquid semen was to be favorable to the production of females; thick semen produced males. According to modern theories, based upon observation of invertebrate animals (O. Hertwig, Balfour, Landois, Minot, and others), it appears improbable that this position can be maintained. The supporters of this theory assert that a single spermatozoon suffices for the fertilization of an ovule, or to develop the ovum into a so-called “oosperm,” that is to say, to form a really fertilized ovum. (Perhaps the excess of semen serves for the earliest nutritive processes of the ovum; which would, however, be difficult to prove.) This fact has been also confirmed in the case of the higher animals, and it might be in a similar manner brought to an issue in the case of man. However, observations of this kind have not yet proved possible with man. But in the case when several spermatozoa penetrate the interior of a single ovum, anomalies in the process of development result from the formation of several nuclei. Such ova, also, perhaps in consequence of excess of semen, are very often aborted and perish.
In order to throw light on the causes determining sex, Pflüger (in connection with results obtained by Born, which will be cited later) attempted to determine the relative numbers of the sexes, under normal conditions, in the case of the frog (Rana fusca). The numbers were taken by his pupils, A. von Griesheim and Dr. W. Kochs. The identification of the sex was made with a microscope under the supervision of Pflüger. According to Pflüger the Graafian follicles are easily identified with the aid of a microscope, if they are not in their earliest stage. They contain an ovum with a scanty yolk and large germinal vesicles with germinal markings. The whole is surrounded by connective tissue.