EPITHELIUM. 



239 



Fig. 142. 



increasing in number and development as the vessels increase in 

 size, may be the rudiments of epithelial cells. Fig. 

 142 shows the epithelium of the lymphatic vessels. 



The epithelial cells of the salivary glands contain 

 a greater amount of fatty and pigment-granules than 

 occur in most mucous glands. 



The cells of the seminiferous tubes are smaller 

 before puberty. At that period they increase, and 

 assume a higher function the secretion of semen. 

 They merge into conoidal epithelium at the head of 

 the epididymis, as already stated. 



The epithelium of the left ventricle and auricle of 

 the horse is seen in Figs. 143 and 144. 



The epithelium of the Graafian vesicle constitutes 

 what is termed the "membrana granulosa," and con- 



Nucleated epithe- 

 lial cells of lympha- 

 tics of a horse. (Mag- 

 nified 320 diameters . ) 



Fig. 143. 



Fig. 144. 



Epithelium of left ventricle of a horse. 

 (Magnified 200 diameters.) 



Epithelium of left auricle of a horse, showing the 

 rounded and the pointed forms of the cells. (Magnified 

 200 diameters.) 



sists of roundish, polygonal, nucleated cells, 3^3 to ^g 1 ^ of an inch 

 in diameter. They become club-shaped about the time the ovum 



Fig. 145. 



Membrana granulosa of ovum of bitch during heat. A. The elongated form and stellate arrange- 

 ment of its cells around the zona pellucida. B. The same ovum after the removal of moat of its 

 club-shaped cells. 



