234 ELEMENTARY BIOLOGY. [xill. 



/3. The clear round holes, scattered about ; these 

 are sections of glomeruli from which the con- 

 tained vessels have fallen out. Some may be 

 seen in which a granular mass still lies. 



h. Examine with a higher power — • 



a. The epithelium lining the tubules, composed in 

 some of granular and ill-defined cells, in other 

 (usually larger) tubules of clearer and better 

 defined cells ; both varieties are nucleated. 



c. Examine specimens of injected kidney with a 

 low power. Note the vascular tufts of the 

 glomeruli. 



k. The testis. 



1. Imbed a testis which has been hardened in alcohol : 

 cut sections and mount in glycerine. 



a. Examine with a low power. 



a. The organ is chiefly made up of tortuous 

 tubules, which are seen cut in various direc- 

 tions. 



h. Examine with a high power. 



a. Note the epithelium lining the tubules : it 

 varies with the season of the year (whether 

 before or after the breeding time), and is 

 usually extremely granular and ill-defined. 

 The cells are arranged in two or three rows, 

 and at the time of breeding the most superfi- 

 cial layer of cells is transformed into sperma- 

 tozoa, each cell giving rise to several. These 

 lie side by side at right angles to the lumen of 



