344 



STRUCTURE OF THE MAMMA. 



Fatty granules are formed in this part of the cell and are afterwards extruded. 

 The decomposed portion of the cell is dissolved in the milk, and the fatty granules 

 become free as milk-globules (fig. 234, II, a). If nuclei are present in that part of 

 the cell which is broken up, they also pass into the milk and give rise to the presence 

 of nuclei n in the secretion. . 



Besides the milk-globules and colostrum corpuscles, Rauber has found leucocytes undergoing 

 fatty dcgen'^tion and single pale cells (/). Occasionally milk-globules are found with traces 

 of the cell-substance adhering to their surface (b). ,._.,. ... . - . 



Fonnktion of Milk. -Concerning the formation of the mdividual constituents of milk H. 

 Thierfelder, who digested fresh mammary glands directly after death found that during the 

 digestion of the glands, at the temperature of the body, a reducing substance, probably lactose, 

 wi formed by a process of fermentation. The mother substance (saccharogen) is soluble m 

 water, but not in alcohol or ether, is not destroyed by boiling and is not identical with glycogen. 

 The ferment which forms the lactose is connected with the gland-cells-it does not pass into the 

 milk, nor into a watery extract of the gland. During the digestion of the mammary glands at 

 the temperature of the body, casein is formed, probably from serum-albumin, by a process of 

 fermentation. This ferment occurs in the milk. 



The nipple and its areola are characterised by the presence of pigment more abundant 

 during pregnancy-in the rete Malpighii of the skin, and by large papilla? in the cutis vera 

 Some of the papilla* contain touch -corpuscles. Numerous non-striped muscular fibres surround 

 the milk-ducts in the deep layers of the skin and in the subcutaneous tissue, Ayhich contains no 

 tat These muscular fibres can be traced, following a longitudinal course, to the termination ot 

 the dncts on the surface. The small glands of Montgomery which occur on the areola during 

 lactation, are just small milk-glands, each with a special duct opening on the surface ot the 



Arteries proceed from several sources to supply the mamma, but their branches do not 

 accompany the milk-ducts ; each gland acinus is surrounded by a network of capillaries, which 



I. 



Fig. 234. 

 Inactive acinus of the mamma. II. During the secretion of milk a, b, milk-globules ; 

 c, d, c, colostrum corpuscles ; /, pale cells (bitch). 



communicate with those of adjoining acini by small arteries and veins. The veins of the areola 

 are arranged in a circle (circulus Halleri). The nerves are derived from the supraclavicular, 

 and the 1I-IV-VI intercostals ; they proceed to the skin over the gland, to the very sensitive 

 nipple, to the blood-vessels and non-striped muscle of the nipple, and to the gland acini, where 

 their mode of termination is still unknown. Lymphatics surround the alveoli, and they are 

 often full. The milk appears to be prepared from the lymph contained in the lymphatics 

 surrounding the acini. 



The comparative anatomy of the mamma. The rodents, insectivora, and carnivora have 10 

 to 12 teats, while some of them have only 4. The pachydermata and ruminantia have 2 to 4 

 abdominal teats, the whale has 2 near the vulva. The apes, bats, vegetable- feeding whales, 

 elephants, and sloths have 2, like man. In the marsupials the tubes are arranged in groups, 

 which open on a patch of skin devoid of hair without any nipple. The young animals remain 

 within the mother's pouch, and the milk is expelled into their mouths by the action of a 

 muscle the compressor mammae. 



The development of the human mamma begins in both sexes during the third month ; at the 

 fourth and fifth months a few simple tubular gland-ducts are arranged radially around the 

 position of the future nipple, which is devoid of hair. In the new-born child the ducts are 

 branched twice or thrice, and are provided with dilated extremities, the future acini. Up to 

 the twelfth year, in both sexes, the ducts continue to divide dendritically, but without any 

 proper acini being formed. In the girl 'at puberty, the ducts branch rapidly ; but the acini 

 are formed only at the periphery of the gland; during pregnancy, acini are also formed in the 



