THE FEMALE BREAST milk-glands are developed in the same manner as are the glands of the skin, and arise like these from the stratum Malpighii cutis. They appear very early in embryonic life, probably at the beginning of the third month. First, an oval thickening of the stratum Malpighii is noticeable; the accumulation of cells becomes constantly greater, and gradually takes On the form of a plump club shaped mass, which in a later stage puts forth short compact buds, these gradually becoming longer and more slender. Toward the end of the fifth month sprouts are again given out from the buds. The first broad epithelial growth now begins to disappear, and the primary buds be come ducts, which in increased numbers reach out toward the superficial layers. Through continued division of the cell ducts a constantly greater differentiation arises, which, however does not exceed a certain propor tion. This stage concludes the preliminary formation of the milk-glands.
In boys and girls alike the condition remains as described, until in the latter new stimulants to growth occur from the influence of puberty. The specialized gland elements, as well as the surrounding connective tissue stroma and the subcutaneous fat, increases rapidly, this increase being greater, however, in the two components last named.
The normally developed organ of the virgin contains the corpus surrounded by a rich layer of fat, and is composed of firm white glistening connective tissue, in which the epithelial gland constitu ents are so sparingly intermingled that they are not to be found in every microscopical field. The cells are found in a single layer and are flattened.
The situation is changed immediately with the beginning of preg nancy. At this time an exceedingly active proliferation commences, which differs, however. from that noted in development of the organs during puberty, in that the parenchymatous epithelial elements are most active in reproduction. The tubular glands develop new- sprouts every where; the surrounding connective tissue, previously so poor in nuclei, 345 becomes richly impregnated with leucocytes and mast-cells; the active cell changes mentioned produce a corresponding manifold mitosis.
Parallel with these processes is found a very rich blood supply and the breasts are considerably increased in size and are turgescent. Under the skin the swollen veins are to be seen running a tortuous course.
At the time of delivery the development ceases. During lactation there is no further increase of parenchyma. Diligent research shows no further cell division. The completely formed organ is now either spheri cal or conical in form (Figs. o and c, Plate 1). The nipples are in most cases prominent, arising abruptly from the inner margin of the areola. Infrequently, to be sure, they are found less developed; and in rare cases there arc no nipples, but in their place there is usually a groove like depression, at the bottotn of which the milk-glands empty themselves. This condition shows au arrested development, since the milk-ducts originally end in a shallow- depression, the floor of which is gradually elevated, thus becoming the nipple.
When a puerperal mammary gland which has been hardened in a 10 per cent. formalin solution is opened by a median sagittal incision, on the inner surface will be seen the prominent true gland bodies, the paren chyma islands, surrounded by subcutaneous fat and divided by con nective tissue septa, which become broader as they approach the nipple, uniting behind it (in well developed bodies) to form a thick knot of con nective tissue. These knots vary greatly in size, and may be so large that the acini appear to be attached as appendices to them.
The supporting Aroma contains lactiferous ducts, ten to fifteen in number, which in the central portion of the fibrinous knot described above become widened into an ampulla of a few millimetres in diameter (Fig. 51.), separated for the most part, which then empty at the top of the nipple. Each of the lactiferous ducts corresponds to a particular gland, so that these ten to fifteen completely separate and similar bodies compose the organ.