THE MAMMAEY GLANDS. 1337 



lies upon the superficial aspect of the pectoralis major and to a less extent upon the 

 serratus anterior muscle. Near the summit of each mammary elevation, and usually 

 at the level of the fourth or fifth rib, is placed the wart-like nipple .or papilla 

 mammae, which is pierced by the minute openings of the lactiferous ducts and is 

 surrounded by a coloured circular area of skin called the areola. The skin 

 covering the nipple is thrown into numerous wrinkles, and on the areola exhibits 

 many minute rounded projections due to the presence of underlying cutaneous 

 glands. These have received the name of glandulas areolares, and are considered to 

 represent rudimentary portions of the mamma. The colour of the nipple and 

 areola varies with the complexion of the individual, but in young subjects they 

 are usually of a somewhat rosy-pink colour, which changes to a deep brown during 

 the second and third months of first pregnancy. Also, during pregnancy, the 

 areola increases in size and its glands become more marked. The nipple contains 

 a considerable number of unstriped muscle fibres, and becomes firmer and more 

 prominent as a result of mechanical stimulation. 



The size and appearance of the mammae vary much, not only in the different 

 races of mankind, but also in >the same individual under different conditions. In 

 the young child the mammae are small, and there is little difference between those 

 of the male and female. Their growth is slow until the approach of puberty, 

 and then the female mammas increase rapidly in size. At each pregnancy 

 the mammae become large, and they attain their greatest development during 

 lactation. The size of the 

 mamma depends partly on the 

 amount of superficial fat and 

 partly on the amount of gland- 

 ular tissue present. 4 



Structure of the Mamma. \ 



The mamma is composed of 

 a mass of glandular tissue 

 traversed and supported by 

 strands of fibrous connective 

 tissue, and covered by a thick 

 layer of fat. The glandular 

 tissue, to which the term corpus 

 mammae is applied, forms a 

 somewhat conical mass whose 

 apex corresponds to the posi- 

 tion of the nipple while its 

 base is loosely connected to the 



fascia covering the pectoralis FIG 105L _ DlsSECTION OF THE MAMMA . 



major and serratus anterior 



muscles. In section the corpus mammae is readily distinguished from the sur- 

 rounding fat by its firmer consistency and by its pinkish- white colour. The corpus 

 mammae is composed of lobes and lobules, and its superficial aspect- and edges are 

 very uneven, the inequalities of its surface being filled up by processes of the fatty 

 tissue which forms a covering for the gland. This fatty covering is incomplete 

 beneath the areola, and here the lactiferous ducts pass into the nipple. The 

 gland is composed of fifteen to twenty lobes, or lobi mammas, which radiate 

 from the nipple, each lobe being quite distinct from the others and possessing 

 its own duct. The lobes are subdivided into secondary lobes and lobules, bound 

 together and supported by a considerable amount of connective tissue which forms 

 the stroma of the gland. 



The alveoli of the gland and the secretory epithelium lining them vary 

 much under different conditions. At puberty the corpus mammae is composed 

 chiefly of connective tissue stroma and the ducts of the gland. At this time 

 the alveoli are small and few in number. During lactation, when the gland is 

 fully functional, the alveoli are enlarged, distended with fluid, and much more 

 numerous. The epithelial cells are cubical and filled with fat globules. When 

 the gland is not secreting, the alveoli become small and reduced in number 



