CASTOR 



543 



of crystalline calcium carbonate can be detected, often in consider- 

 able quantity. The secretion varies much both in quantity and 



FIG. 249. Sexual organs ofjnale Beaver, showing 

 the position of the two castor sacs, c, com- 

 municating by a common aperture with the 

 preputial canal. The latter and one of the 

 castor sacs have been opened, t, testicle ; 

 u, urethra ; c, castor sacs ; g, gland of penis ; 

 p, penis ; r, rectum ; a, anus ; e, anal gland ; 

 d, aperture of anal gland ; o, preputial orifice ; 

 /, undersurf ace of tail. (Moeller, after Brandt. ) 



appearance, being sometimes pale in colour and soft, sometimes 

 hard and dark. 



