PHYSIOLOGICAL ANATOMY OF THE MAMMARY GLANDS 291 



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 papillae, which are largely developed near the summit. 

 It is covered with epithelium in several layers, the lower strata being 

 rilled 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-follicles or sudoriparous glands. These 

 glands are of the racemose variety and not in the form of simple follicles. 

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

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

 cular fibres have no definite direction, but are so abundant that when 

 contracted the nipple becomes firm and hard. 



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

 gland, on a bed of adipose tissue, but it is closely adherent to the sub- 

 jacent glandular 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 and lies on 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 areola presents the following 

 structures : papillae, considerable smaller than those on the nipple ; hair- 

 follicles, containing small rudimentary hairs ; sudoriparous glands ; and 

 sebaceous glands connected with the hair-follicles. The sebaceous 

 glands are large, and their situation is indicated by little prominences 

 on the surface of the areola, which are especially marked during 

 pregnancy. 



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

 is covered in front with a subcutaneous layer of fat, and posteriorly it is 

 enveloped in a fibrous membrane loosely attached to the pectoralis major 

 muscle. A considerable quantity of adipose tissue also is found in the 

 substance of the gland between the lobes. 



Separated from the adipose and fibrous tissue, the mammary gland 

 is found divided into lobes, fifteen to twenty-four in number. These 

 are subdivided into lobules made up of a greater or less number of acini. 

 The secreting structure is of a reddish yellow color and is distinctly 

 granular, presenting a decided contrast to the pale and uniformly 

 fibrous appearance of the gland during the intervals of lactation. If 

 the ducts are injected from the nipple and followed into the substance 

 of the gland, each one will be found distributing its branches to a dis- 



