4 THE TESTIS AND ITS RELATION TO REPRODUCTION 



4. Function of the seminal vesicles (vesicular glands) 



5. Function of the prostate gland 



6. Bulbourethral (Cowper's) glands 



7. Functions of seminal fluid 



a. Amount of seminal fluid discharged and its general functions 



b. Coagulation of the semen 



c. Hyaluronidase 



d. Accessory sperm 



e. Fructose 



f. Enzyme-protecting substances 



D. Internal and external factors influencing activities of the testis 



1. Internal factors 



a. Temperature and anatomical position of the testis 



b. Body nourishment in relation to testicular function 



c. The hypophysis and its relation to testicular function 



2. External environmental factors and testis function 



a. Light as a factor 



b. Temperature influences 



E. Internal factors which may control seasonal and continuous types of testicular 

 function 



F. Characteristics of the male reproductive cycle and its relation to reproductive con- 

 ditions in the female 



A. Introduction 



1. General Description of the Male Reproductive System 



The male reproductive system of most vertebrate animals consists of two 

 testis with a sperm-conveying duct and attendant auxiliary glands associated 

 with each testis. In some species, such as the frog and many teleost fishes, the 

 sperm-conveying duct is a simple structure, but in most vertebrate forms there 

 is a tendency for the duct to be complicated. The cyclostomatous fishes do not 

 possess sperm-conveying ducts from the testis to the outside. 



In reptiles, some birds and all mammals, in gymnophionan amphibia and 

 in the "tailed" frog, Ascaphus, in sharks and certain teleost fishes, an intro- 

 mittent organ is added to the sperm-conveying structures for the purpose of 

 internal fertilization. But an intromittent organ is not present in all species 

 which practice internal fertilization. In many salamanders, internal fertiliza- 

 tion is effected by the spawning of a spermatophore filled with sperm; the 

 latter is picked up by the cloaca of the female. The sperm in these salamanders 

 are stored in special pockets or tubules within the dorsal wall of the cloaca. 

 These storage tubules form the spermatheca (fig. 10). Direct transfer of sperm 

 to the female by cloacal contact may occur in some species. 



2. Importance of the Testis 



The word testis or testicle was formerly applied to the ovary of the female, 

 as well as to the male sperm-producing organ, and the term "female testicle" 



