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The supposed fact that female secondary characters in Vertebrates are absent in the male is completely disproved for Mammals by the presence of rudimentary mammary glands in the male. It is true that secondary sex-characters are usually positive in the male, while those of the female are apparently negative, but in the case of the mammary glands the opposite is the case.
It is that of the mouth of the young kangaroo. Now the kangaroo is born in such an exceedingly imperfect and undeveloped condition, that it is quite unable to suck. The mother therefore places the minute blind and naked young upon the nipple, and then injects milk into it by means of a special muscular envelope of the mammary gland.
In fine, two quite characteristic features of the Mammals, which distinguish them not only from the birds and reptiles, but from all other animals, are the possession of a complete diaphragm and of mammary glands that produce the milk for the nutrition of the young.
This remarkable woolly coat of the human embryo is a legacy from the apes, our ancient long-haired ancestors. Mammary gland of a new-born infant, a original central gland, b small and c large buds of same. It is not less noteworthy that many of the higher apes approach man in the thinness of the hair on various parts of the body.
When this is realized, and the fact that vaccination dries up the mammary glands is taken into account, is it not time to pause and consider? The figures of this one small concern represent the report of only one out of several hundred such firms doing business in all parts of the country. Some years ago, a disease similar to smallpox broke out among the sheep in certain parts of Scotland.
Boston Soc. of Nat. Hist. Sept. 15, 1857; also Prof. Turner, in 'Journal of Anatomy and Physiology, Nov. 1, 1866, p. 78. Dr. But the above suggestion first occurred to me from mammary glands of male mammals being so much more perfectly developed than the rudiments of the other accessory reproductive parts, which are found in the one sex though proper to the other.
The development of the mammary glands would have been of no service, and could not have been affected through natural selection, unless the young at the same time were able to partake of the secretion.
He who would therefore in this science undertake the proclamation of absolute and immutable truths must be content with such platitudes as the following: "All men must die; all female mammals have mammary glands, etc."
Uterine and mammary functions are generally regarded as essentially female characteristics, and are included in the popular idea of the sex of woman. Scientifically, of course, they are not at all necessary or universal features of the female sex, but are peculiar to the mammalian class of Vertebrates in which they have been evolved.
They have the mammary part of the milk-mirror well developed, but the perinean part contracted, or wholly wanting, as in cut G; or both parts of the mirror are moderately developed, or slightly indented, as in cut H. Cut E belongs also to this class, in the lower part; but it indicates a cow, which as the upper mirror, 1, indicates dries up sooner when again in calf.
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