THE FEMALE GENITAL OBOANS. 



885 



a certain number of principal canals : these open into the galactoferous sinuses 

 (each a sacculus vel sinus lactiferus). The glandular culs-de-sac are lined 

 with a polyhedral epithelium, which becomes spherical and infiltrated with 

 fat during lactation. 



Fig. 413. 



Fig. 414. 



GLAND-VESICLES, WITH THEIR EXCRETOKY ULTIMATE FOLLICLES, OR GLAND VESICLES, 



DUCTS TERMINATING IN A DUCTUS LAO- WITH THEIR EPITHELIUM OK SECRETING 



TIPEROUS; PROM A MERCURIAL INJECTION; CELM, a, a, AND NUCLEI, 6,6, 

 MAGNIFIED FOUR TIMES. 



Placed at the base of the teat, the galactoferous sinuses or reservoirs are 

 generally two in number, but sometimes there are three, and even four ; 

 they nearly always communicate with each other, and are continued into the 

 mammilla by an equal number of independent excretory canals — the definitive 

 ducts, whose orifices are very small, and are seen beside each other at the free 

 extremity of the teat. A fine mucous membrane lines the inner face of this 

 excretory apparatus ; it is doubled in the teat by a thick layer of tissue, 

 which again is covered by the skin that adheres closely to it. (Between 

 the external and internal tunic of the teats, are found numerous fasciculi 

 of unstriped muscular fibres, arranged in a circular and longitudinal manner 

 aroimd these ducts.) 



Connective tissue, vessels and nerves, complete this organisation. (The 

 arteries are from the external pudic trunk ; the veins are very numerous, and 

 pass to the trunk of the same name ; 



the nerves are derived from the first ^'S- 415. 



lumbar pair.) 



Functions. — The mammre secrete 

 the milk ; they undergo remarkable 

 modifications at puberty and at the 

 end of each gestation — modifications 

 which are related not only to their 

 volume and secretion, but also to 

 their minute structure. After ges- 

 tation, the gland- vesicles shrink: 

 become, as it were, atrophied, and 

 Lave only a polygonal epithelium. 

 At the termination of gestation, they 

 are enlarged, new vesicles are de- 

 veloped, and the epithelium changes 

 its character : filling the gland cavi- 

 ties, assuming a spherical shape, and 

 becoming charged with fat granula- 

 tions. The period of lactation being 

 completed, the mammae take on their 

 former character. (In Mares which 

 have not been bred from, the mamm£B are hard and small, the teats but 

 elightly prominent, and the glandular tissue scanty. In old brood-mares, 

 69 





MICROSCOPIC APPEARANCE OP MILK, WITH AH 

 INTERMIXTURE OF COLOSTRIC CORPUSCLES 

 AT a, a, AND ELSEWHERE. 



