THE MAMMM 1267 



The Mammae (Mammary Gland; Breasts). 



The mammae secrete the milk, and are accessory glands of the generative system. 

 They exist in the male as well as in the female; but in the former only in the rudi- 

 mentary state, unless their growth is excited by peculiar circumstances. In the 

 female they are two large hemispherical eminences lying within the superficial 

 fascia and situated on the front and sides of the chest; each extends from the second 

 rib above to the sixth rib below, and from the side of the sternum to near the mid- 

 axillary line. Their weight and dimensions differ at different periods of life, and 

 in different individuals. Before puberty they are of small size, but enlarge as the 

 generative organs become more completely developed. They increase during preg- 

 nancy and especially after delivery, and become atrophied in old age. The left 

 mamma is generally a little larger than the right. The deep surface of each is 

 nearly circular, flattened, or slightly concave, and has its long diameter directed 

 upward and lateralward toward the axilla; it is separated from the fascia covering 

 the Pectoralis major, Serratus anterior, and Obliquus externus abdominis by loose 

 connective tissue. The subcutaneous surface of the mamma is convex, and presents, 

 just below the center, a small conical prominence, the papilla. 



The Mammary Papilla or Nipple (papilla mammce) is a cylindrical or conical 

 eminence situated about the level of the fourth intercostal space. It is capable 

 of undergoing a sort of erection from mechanical excitement, a change mainly 

 due to the contraction of its muscular fibers. It is of a pink or brownish hue, its 

 surface wrinkled and provided with secondary papillae; and it is perforated by from 

 fifteen to twenty orifices, the apertures of the lactiferous ducts. The base of the 

 mammary papilla is surrounded by an areola. In the virgin the areola is of a delicate 

 rosy hue; about the second month after impregnation it enlarges and acquires a 

 darker tinge, and as pregnancy advances it may assume a dark brown or even black 

 color. This color diminishes as soon as lactation is over, but is never entirely 

 lost throughout life. These changes in the color of the areola are of importance 

 in forming a conclusion in a case of suspected first pregnancy. Near the base of 

 the papilla, and upon the surface of the areola, are numerous large sebaceous glands, 

 the areolar glands, which become much enlarged during lactation, and present 

 the appearance of small tubercles beneath the skin. These glands secrete a pecu- 

 liar fatty substance, which serves as a protection to the integument of the papilla 

 during the act of sucking. The mammary papilla consists of numerous vessels, 

 intermixed with plain muscular fibers, which are principally arranged in a circular 

 manner around the base: some few fibers radiating from base to apex. 



Development. The mamma is developed partly from mesoderm and partly from 

 ectoderm its bloodvessels and connective tissue being derived from the former, its 

 cellular elements from the latter. Its first rudiment is seen about the third month, 

 in the form of a number of small inward projections of the ectoderm, which invade 

 the mesoderm; from these, secondary tracts of cellular elements radiate and sub- 

 sequently give rise to the epithelium of the glandular follicles and ducts. The 

 development of the follicles, however, remains imperfect, except in the parous 

 female. 



Structure (Figs. 1172, 1173). The mamma consists of gland tissue; of fibrous tissue, con- 

 necting its lobes; and of fatty tissue in the intervals between the lobes. The gland tissue, when 

 freed from fibrous tissue and fat, is of a pale reddish color, firm in texture, flattened from before 

 backward and thicker in the center than at the circumference. The subcutaneous surface of 

 the mamma presents numerous irregular processes which project toward the skin and are joined 

 to it by bands of connective tissue. It consists of numerous lobes, and these are composed of 

 lobules, connected together by areolar tissue, bloodvessels, and ducts. The smallest lobules 

 consist of a cluster of rounded alveoli, which open into the smallest branches of the lactiferous 

 ducts; these ducts unite to form larger ducts, and these end in a single canal, corresponding with 

 one of the chief subdivisions of the gland. The number of excretory ducts varies from fifteen 



