278 THE MAMMARY GLANDS, BY C. LANGER. 



ones, nor can the whole gland ever be broken up into large 

 lobules, corresponding to the several excretory ducts, because 

 the stroma of the gland is composed of a firm and undivided 

 mass of connective tissue, that only becomes somewhat looser 

 near the periphery, in order to invest and isolate the lobules of 

 the gland that are there present. Lamellae of the stroma, given 

 off from the margins and upper surface of the organ, join with 

 the subcutaneous connective tissue to form. nooks and capsules 

 that are occupied by the surrounding fat. The solid nucleus 

 of the gland, therefore, is in immediate union with the skin 

 only at the nipple ; at this point, and beneath the areola, no 

 adipose tissue exists, but in its place there is a thick layer of 

 smooth muscular fibres. 



The structure of the excretory ducts is very simple ; their 

 walls consisting of finely fibrous connective tissue, which is 

 more dense externally, with a circular disposition of the fibres, 

 the outermost layer being intermingled with many elastic 

 fibres. They have no proper muscular system ; their epithe- 

 lium is composed of small columnar cells. The larger ducts, 

 when empty, collapse, the thin walls falling into longitudinal 

 folds, which give them an irregularly distended or stellate form 

 on section. 



The gland vesicles are lined by a single layer of epithelium, 

 which at their fundus is composed of small polyhedric cells, 

 but near their neck of somewhat higher cells that sometimes 

 bound a very small central space. The entire cavity of 

 the acinus is filled with fat drops, the anatomical constituent 

 of the milk; and although the contents of these acini are 

 easily removed, many fat drops always remain adherent to 

 the epithelium, and some may even be found distributed 

 between the nuclei of the epithelial cells. In puerperal women 

 who have died soon after delivery, the gland vesicles con- 

 tain a few milk spheroids sparingly interspersed amongst the 

 closely compressed epithelial cells. If the fat be extracted 

 from the contents of the acini by means of aether, a plexus 

 traversing the acinus in all directions is formed by the 

 coagulated caseous substance with spaces corresponding to the 

 fat drops that have been removed. Connective tissue constitutes 

 another element of the wall of the acini, and with its cellular 



