THE MAMMARY GLANDS. 613 



the furrow diverge posteriorly, running at the sides of the 

 genito-urinary orifice internally to the cutaneous folds just 

 mentioned (see Fig. 245, B, D). In the female, this body be- 

 coming retracted, forms the clitoris, and the margins of the 

 furrow on its under surface are converted into the nymphse, or 

 labia minora, the labia majora pudendse being constituted by 

 the great cutaneous folds. In the male foetus, the margins of 

 the furrow at the under surface of the penis unite at about the 

 fourteenth week, and form that part of the urethra which is 

 included in the penis. The large cutaneous folds form the 

 scrotum, and at a later period, namely, in the eighth month 

 of development, receive the testicles, which descend into them 

 from the abdominal cavity. Sometimes the urethra is not 

 closed, and the deformity called hypospadias then results. The 

 appearance of hermaphroditism may, in these cases, be in- 

 creased by the retention of the testes within the abdomen. 



The Mammary Glands. 



The mammary glands, which may be considered as organs 

 superadded to the reproductive system in man and other mem- 

 bers of the class (Mammalia) which derives its name from 

 them, are, in the essential details of their structure, very simi- 

 lar to other compound glands, as the pancreas and salivary 

 glands ; that is to say, they are composed of larger divisions 

 or lobes, and these are again divisible into lobules, the lob- 

 ules being composed of the follicular extremities of ducts, 

 lined by glandular epithelium. The lobes and lobules are 

 bound together by areolar tissue ; while, penetrating between 

 the lobes, and covering the general surface of the gland, with 

 the exception of the nipple, is a considerable quantity of yellow 

 fat, itself lobulated by sheaths and processes of tough areolar 

 tissue (Fig. 246) connected both with the skin in front and 

 the gland behind ; the same bond of connection extending also 

 from the under surface of the gland to the sheathing connec- 

 tive tissue of the great pectoral muscle on which it lies. The 

 main ducts of the gland, fifteen to twenty in number, called the 

 lactiferous or galactophorous ducts, are formed by the union of 

 the smaller ducts, and open by small separate orifices through 

 the nipple. Just before they enter the base of the nipple, these 

 ducts are dilated (6, Fig. 246) ; and, during lactation, the period 

 of active secretion by the gland, they form reservoirs for the 

 milk, which collects in them and distends them. The walls of 

 the gland-ducts are formed of areolar and elastic tissue, and 

 are lined, internally by a fine mucous membrane, the surface 

 of which is covered by squamous or spheroidal epithelium. 



52 



