246 



HAND-BOOK OF PHYSIOLOGY. 



IMPREGNATION OF THE OVUM. 

 MALE SEXUAL FUNCTIONS. 



Testes. The fluid of the male, by which the ovum is impregnated, 

 consists essentially of the semen secreted by the testicles: and to this are 

 added, as necessary, perhaps, to its perfection, a material secreted by the 

 vesiculce seminales, as well as the secretion of the prostate gland, and of 

 Cowper's glands. Portions of these several fluids are, probably, all dis- 

 charged, together with the proper secretion of the testicles. 



The secreting structure of the testicle and its duct are disposed of in 

 two contiguous parts, (1) the body of the testicle enclosed within a tough 



FIG. 400. 



FIG. 401. 



FIG. 400. Section of a dog's epididymis. The tube is cut in several places, both transversely and 

 obliquely; it is seen to be lined by a ciliated epithelium, the nuclei of which are well shown, c, con- 

 nective tissue. (Schofield.) 



FIG. 401. A section of dog's testicle, highly magnified, showing three "tubuli seminiferi," lined 

 and largely occupied by a spheroidal epithelium, the numerous nuclei of which are well seen ; c, con- 

 nective tissue surrounding and supporting the tubuli; sp, masses of spermatozoa occupying' the 

 centre of tubuli: the small black bodies scattered about are the heads of the spermatozoa. (Scho- 

 field.) , 



fibrous membrane, the tunica albuginea, on the outer surface of which 

 is the serous covering formed by the tunica vaginalis, and (2) the epi- 

 didymis and vas deferens. 



Vas Deferens. The vas deferens, or duct of the testicle, which is 

 about two feet in length, is constructed externally of connective tissue, and 

 internally is lined by mucous membrane, covered by columnar epithe- 

 lium; while between these two coats is a middle coat, very firm and 



