Vietnam or Thailand ? Vote for the TOP Country of the Week !
Updated: June 1, 2025
It is a well-established fact that auto-erotic manifestations may sometimes be observed even in infants of less than twelve months. We are not now called upon to discuss the disputable point as to how far such manifestations at this age can be called normal. A slight degree of menstrual and mammary activity sometimes occurs at birth.
These are generally developed in one sex and rudimentary in the other. Thus the spermaducts are formed from the Wolffian ducts in the male, whereas in the female we have merely rudimentary traces of them in Gaertner's canals. Again, the male has in his nipples and mammary glands the rudiments of organs that are usually active only in the female.
When we treat of sexual selection, we shall meet with innumerable instances of this form of transmission, as in the case of the spurs, plumes, and brilliant colours, acquired for battle or ornament by male birds, and inherited by the females in an imperfect or rudimentary condition. The possession by male mammals of functionally imperfect mammary organs is, in some respects, especially curious.
This conclusion is supported by what is known of their manner of development; for Professor Turner informs me, on the authority of Kolliker and Langer, that in the embryo the mammary glands can be distinctly traced before the nipples are in the least visible; and the development of successive parts in the individual generally represents and accords with the development of successive beings in the same line of descent.
The mammary glands of the Ornithorhynchus may be considered, in comparison with the udders of a cow, as in a nascent condition. The ovigerous frena of certain cirripedes, which have ceased to give attachment to the ova and are feebly developed, are nascent branchiae.
A similar, but still stronger, argument may be based upon the existence of teats, and even functional mammary glands, in male mammals. Numerous cases of "Gynaecomasty," or functionally active breasts in men, are on record, though there is no mammalian species whatever in which the male normally suckles the young.
The mammary glands are common to the whole class of mammals, and are indispensable for their existence; they must, therefore, have been developed at an extremely remote period, and we can know nothing positively about their manner of development. Mr.
And in this case, the individuals which secreted a fluid, in some degree or manner the most nutritious, so as to partake of the nature of milk, would in the long run have reared a larger number of well-nourished offspring, than would the individuals which secreted a poorer fluid; and thus the cutaneous glands, which are the homologues of the mammary glands, would have been improved or rendered more effective.
In the female especially there is a cycle of increased activity just prior to her development into the procreative state. During this time secondary sexual characters are developed the pelvis expands, the ovaries and the uterus grow rapidly, the mammary glands develop.
Now, if in the castrated male is transplanted an ovary, the positive characteristics of the female are evoked, such as enlarged mammary glands, and a tendency to secretion of milk. Experiments have also been reported in which a uterus was also placed in such an animal, with a means of entry, and pregnancy followed.
Word Of The Day
Others Looking