442 THE FEMALE EEPRODUCTIVE ORGANS 



thus found their way into the lumen, where they take on a phago- 

 cytic activity and continue their growth. The following facts may 

 be mentioned in support of this theory : #, leucocytes can be read- 

 ily found between the cells of the alveolar epithelium as well as in 

 the lumina of the saccules ; #, the colostrum corpuscles examined 

 in a fresh condition on a warmed slide have been repeatedly shown 

 to possess the property of amoeboid motion ; e, the colostrum cor- 

 puscles, when stained, present the same granular and non-granular 

 varieties as do the leucocytes of the blood ; d, finally, the colostrum 

 corpuscles have been shown to undergo mitotic cell division (Biz- 

 zozero and Ottolenghi *), a phenomenon which we should hardly ex- 

 pect to find in degenerated and desquamated epithelial cell remnants. 



The Uood vessels of the mammary gland are specially abun- 

 dant. They form rich capillary plexuses about the walls of the 

 active alveoli. Many of the venules coming from these plexuses 

 converge toward the areola, where they form an incomplete venous 

 circle (circulus venosus of Holler) from which the efferent veins 

 take their origin. 



The lymphatics of the mammary gland are also numerous. 

 They take origin from broad channels among the alveoli and enter 

 a rich plexus about the interlobular ducts. From here several 

 vessels pass to the lymphatic nodes of the axilla. 



The nerves of the mammary gland are distributed to the vas- 

 cular walls, to the smooth muscle of the areola and nipple, to the 

 alveolar epithelium, and in the connective tissue of the nipple and 

 areola they occasionally terminate in tactile and Pacinian corpuscles. 



Among the secreting alveoli the nerve fibres form an epilemmal 

 plexus beneath the membrana propria, from which fibrils pene- 

 trate between the epithelial cells, upon which they end in minute 

 granular varicosities ( Arnstein f ). 



MILK 



Milk, secreted by the active mammary gland, consists of an 

 emulsion, in which fat droplets, varying in size from 2 ft to 20 /A 

 or more, are suspended in a watery albuminous fluid. Each fat 

 droplet is presumably invested with a thin coat of casein, derived 

 from the cytoplasm of the secreting epithelium. Occasionally 

 leucocytes occur in the milk, but never in large numbers, and 

 like the similar colostrum corpuscles, they are mostly confined to 

 the -earlier periods of lactation. 



* Ergeb. d. Anat. u. Entwickl., 1899. f A nat. Anz., 1895. 



