280 



THE COMPLETE GRAZIER. 



BOOK II. 



reservoir, which becomes distended with milk as the secretion accumu- 

 lates. Into each of the four milk cisterns innumerable tubes open. 

 Any one of these may be traced back into minute tubes or ducts, 

 which end blindly in several small sacs or bags, and it is these latter 



M 



ms 





fcf 



Fig. 68. 'Section of Udder and Teat of Cow ( Tharihoffier). 



Ma, gland substance ; B, nipple or teat ; ms, acini of gland ; tj, milk ducts ; C, milk- 

 cistern ; r, folds in wide milk-ducts ; z, section of sphincter muscle ; kb, external skin ; 

 lei, narrow milk-duct in the nipple. 



which are called alveoli. The delicate walls of the ducts and the 

 alveoli are lined by a single layer of minute living cells, which are the 

 secreting cells of the mammary gland. The whole gland is richly 

 supplied with blood by means of thin-walled blood capillaries, a dense 



1 Figs. 68, 69, and 70 are reproduced by permission from Dr. Meade Smith's "Physiology 

 of the Domestic Animals." London and Philadelphia : F. A. Davis. 



