THE MAMMARY GLANDS. 



to which they respectively belong. The walls of the ducts are composed 

 of areolar tissue, with longitudinal and circular elastic fibres. Both 

 the terminal vesicles and the ducts are lined with short columnar epi- 

 thelium, which passes into the flat kind near the external openings on 

 the nipple. 



Fig. 342. 



Pi"-. 342. — Magnified Views of the Glandular Substance of the Mamma duuino 

 THE PERIOD OF LACTATION (from Henle). 



A, section of a small lobule of the gland, magnified CO diameters ; 1, sti'oma of con- 

 nective tissue supporting the glandular tissue ; 2, terminal ramuscule of one of the gland- 

 tubes ; 3, glandular vesicles. 



B, four glandular vesicles magnified 200 diameters, showing the lining epithelial cells 

 And some milk-globules. 



Difference according to sex. — The mamma begins to be formed 

 as early as the fourth month of foetal life, but its subsequent growth 

 is comparatively tardy. At the third or fourth year of infancy, there is 

 little or no difference in male and female children. The fuller develop- 

 ment of the gland in the female occurs only towards puberty. 



In the adult male the mammary gland and all its parts exist, but 

 quite in a rudimentary state, the gland itself measuring only from six 

 to nine lines across, and two lines thick, instead of four inches and a 

 half wide and one and a half thick, as in the female. Occasionally the 

 male mamma, especially in young subjects, enlarges and gives out a 

 thin watery fluid ; and, in some rare cases, it has secreted milk. (W. 

 Oruber, On the Male Mamma, in Mem. of the Petersburg Acad., 1866.) 



Blood-vessels and Nerves. — The arteries which supply the mam- 

 mary glands are the long thoracic and some other branches of the 

 axillary artery, the internal mammary, and the subjacent intercostals. 

 The veins have the same denomination. Haller described a sort of 

 anastomotic venous circle surrounding the base of the nipple as the 

 circulus venosus. The nerves proceed from the anterior and middle 

 intercostal cutaneous branches. 



Varieties. — Two or even three nipples have been found on one gland. An 

 additional mamma is sometimes met with, and even four or five have been 

 observed to co-exist ; the supernumerary glands being most frequently near the 

 ordinary pair, but sometimes in a distant part of the body, as the axilla, thigh, 

 or back. 



