THE MAMMARY GLANDS. 1039 



muscles by a layer of fascia. The outer surface of the mamma is convex, and 

 presents, just below the centre, a small conical prominence, the nipple (mammilla}. 

 The surface of the nipple is dark-colored and surrounded by an areola having a 

 colored tint. In the virgin the areola is of a delicate rosy hue; about the second 

 month after impregnation it enlarges and acquires a darker tinge, which increases 

 as pregnancy advances, becoming in some cases of 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. 



Lobule unravelled. 



.-1 mpulla. 



Lobule. Loculi in connective tissue. 



FIG. 578. Dissection of the lower half of the female breast during the period of lactation. (From Luschka.) 



The nipple is a cylindrical or conical eminence capable of undergoing a sort 

 of erection from mechanical excitement, a change mainly due to the contraction 

 of its muscular fibres. It is of a pink or brownish hue, its surface wrinkled and 

 provided with papillse, and it is perforated by numerous orifices, the apertures of 

 the lactiferous ducts. Near the base of the nipple and upon the surface of the 

 areoli are numerous sebaceous glands, which become much enlarged during lacta- 

 tion, and present the appearance of small tubercles beneath the skin. These 

 glands secrete a peculiar fatty substance, which serves as a protection to the integu- 

 ment of the nipple during the act of sucking. The nipple consists of numerous 

 vessels, intermixed with plain muscular fibres, which are principally arranged in a 

 circular manner around the base, some few fibres radiating from base to apex. 



Structure. The mamma consists of gland-tissue ; of fibrous tissue, connecting 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, 

 circular in form, flattened from before backward, thicker in the centre than at the 

 circumference, and presenting several inequalities on its surface, especially in front. 

 It consists of numerous lobes, and these are composed of lobules connected together 

 by areolar tissue, blood-vessels, and ducts. The smallest lobules consist of a cluster 

 of rounded alveoli, which open into the smallest branches of the lactiferous ducts ; 

 these ducts, uniting, form larger ducts, which terminate in a single canal, correspond- 

 ing with one of the chief subdivisions of the gland. The number of excretory ducts 



