THE MAMMARY GLANDS OF INFANTS AND THEIR DEVELOPMENT.
Similarly to other cutaneous glands, the mammary glands proceed from a growth of the rete Malpighii, and, so far as observations show, they first appear about the third month. The separate divisions of the gland are disconnected by a process of proliferation, and have a flask or pear shape. They appear a little larger and a little more perfectly formed in newly born children, and are of the same size in both sexes. At the time of their first formation in the foetus, there is a slight excavation at the site of the nipple; but the nipples and the excretory ducts of the gland are developed during foetal life. Newly-born children have indeed toler ably well-developed nipples. Th.Hiker describes certain processes in the gland, which have been hitherto thought to be exceptional, as regu lar and normal. He says, of the mammary glands of newly-born children: " The most striking appearance to be seen in all glands, though to a less extent in boys, is the ectasia or dilatation of a now large, now small num ber of gland-ducts, so that they present a considerable lumen from their external opening to the terminal bulb. In these ducts, the lumen is filled with thrown-off epithelium and a white granular mass, while the pre served epithelium is disposed in layers on the basement membrane." Further on he says: " The above described ectasia of the milk-ducts begins in the first week of life, and frequently goes on to pronounced paren chymatous swelling, which may present the appearance of mastitis with great dilatation of the ducts, so that the whole gland has the appearance of a cavernous organ. In such cases, one never finds simple cylindrical
epithelium, but the ducts either contain few epithelia, which seem to be pressed flat against the parietes of the cavernous space, or we find, what is more frequently the case, stratified epithelium with two or three layers of round cells. The greatly dilated ducts and lobules contain sometimes single epithelial cells, sometimes a granular, yellowish, crumbling mass, consisting of large plates, (changed epithelial cells?) and not taking luematoxylin." " To sum up, we find in the beginning dilatation of the milk-ducts in different degrees as characteristic of the first year, which may reach such a degree that cavernous spaces are formed, against the parietes of which lie the flattened epithelial cells." " This occurrence is, in my opinion, physiological, when it occurs in a moderate degree, but when it occurs in a more marked degree and lasts for a longer time, it becomes pathological, and may be considered a mastitis, which, according to my observations, may lead under certain circumstances to similar wide reaching changes in the whole gland, and must exert an influence upon the further development of the gland. Glands of this character, as shown in Fig. 2, (high-grade cystic dilated gland•ducts, Kolliker), are scarcely ever developed normally afterwards, and the faulty development of the breasts in otherwise well-developed women is very probably due to This mastitis of childhood."