328 SECRETION. 



are penetrated by innumerable ramifications which have gradually been devel- 

 oped as processes from the main duct. It is important to remember, how- 

 ever, that these branches are never so abundant or so long during the inter- 

 vals of lactation as they are when the gland is in full activity. 



Between the fourth and fifth months of uterogestation the mammary 

 glands of the mother begin to increase in size ; and at term they are very 

 much larger than during the unimpregnated state. At this time the breasts 

 become quite hard, and the surface near the areola is somewhat uneven, 

 from the great development of the ducts. The nipple itself is increased in 

 size, the papillae upon its surface and upon the areola are more largely devel- 

 oped, and the areola becomes larger, darker and thicker. The glandular 

 structure of the breasts during the latter half of pregnancy becomes so far de- 

 veloped, that if the child be born at the seventh month, the lacteal secretion 

 may be established at the usual time after parturition. Even when parturi- 

 tion takes place at term, a few days elapse before secretion is fully established, 

 and the first product of the glands, called colostrum, is very different from 

 the fully formed milk. 



The only parts of the covering of the breasts that present any peculiarities 

 are the areola and the nipple. The surface of the nipple is covered with pa- 

 pillaB, which are very largely developed near the summit. It is covered by 

 epithelium in several layers, the lower strata being filled with pigmentary 

 granules. The true skin covering the nipples is composed of inelastic and 

 elastic fibres, containing a large number of sebaceous glands, but no hair-fol- 

 licles or sudoriparous glands. These glands are always of the racemose ta- 

 riety, and they never exist in the form of simple follicles (Sappey). The 

 nipple contains the lactiferous ducts, fibres of inelastic and elastic tissue, 

 with a large number of non-striated muscular fibres. The muscular fibres 

 have no definite direction, but are so abundant that when they are contracted 

 the nipple becomes very firm and hard. 



The areola does not lie, like the general integument covering the gland, 

 upon a bed of adipose tissue, but it is closely adherent to the subjacent gland- 

 ular structure. The skin here is much thinner and more delicate than 

 in other parts, and the pigmentary granules are very abundant in some of 

 the lower strata of epidermic cells, particularly during pregnancy. The 

 true skin of the areola is composed of inelastic and elastic fibres und lies 

 upon a distinct layer of non-striated muscular fibres. The arrangement of 

 the muscular fibres sometimes called the subareolar muscle is quite regular, 

 forming concentric rings around the nipple. These fibres are supposed to 

 be useful in compressing the ducts during the discharge of milk. The 

 areolar presents the following structures ; papilla?, considerably smaller than 

 those upon the nipple ; hair-follicles, containing small, rudimentary hairs ; 

 sudoriparous glands ; and sebaceous glands connected with the hair-follicles. 

 The sebaceous glands are very large, and their situation is indicated by little 

 prominences on the surface of the areola, which are especially marked dur- 

 ing pregnancy. 



The mammary gland itself is of the compound racemose variety. It is 



