34 THE TESTIS AND ITS RELATION TO REPRODUCTION 



selves. Rowlands ('44) and also Leonard and Kurzrok ('46) have shown 

 that a seminal fluid deficient in sperm numbers may fertilize if hyaluronidase 

 extracted from sperm (?) is added to such a weakened sperm suspension. 

 The implication is that the accessory sperm thus may act as "cupbearers" 

 for the one successful sperm in that they carry hyaluronidase which aids in 

 liquefying the follicle cells and other gelatinous coating material around the egg. 



e. Fructose 



An older concept in embryology maintained that sperm were unable to 

 obtain or utilize nourishment after they departed from the testis. More recent 

 investigation has shown, however, that sperm do utilize certain sugar materials, 

 and that their survival depends upon the presence of a simple sugar in the 

 medium in which they are kept. (See Mann, '50.) 



The sugar that is found normally in semen is fructose. It varies in quantity 

 from species to species, being small in amount in the semen of the boar or 

 stallion but considerably larger in quantity in the seminal fluid of the bull, 

 man, and rabbit. The seat of origin of this sugar appears to be the seminal 

 vesicle, at least in man, although the prostate may also be involved, particu- 

 larly in the rabbit and also in the dog. The dog, however, has but a small 

 amount of fructose in the seminal discharge. The real function of seminal 

 fructose "might be as a readily utilizable store of energy for the survival of 

 motile spermatozoa" (Mann, '50, p. 360). 



/. Enzyme-protecting Substances 



Runnstrom (personal communication) and his co-workers have demon- 

 strated that the fertilizing life of sea-urchin sperm is increased by certain sub- 

 stances found in the jelly coat of the sea-urchin egg. Presumably these 

 substances are protein in nature, and, according to Runnstrom, they may 

 act to preserve the enzyme system of the sperm. Similarly, the seminal fluid 

 may act to preserve the enzyme system of the sperm, while en route to the 

 egg, especially within the female genital tract. 



D. Internal and External Factors Influencing Activities of the Testis 



Conditions which influence testicular activity are many. Many of the fac- 

 tors are unknown. Nevertheless, a few conditions which govern testis function 

 have been determined, especially in certain mammalian species. The general 

 results of experimental determination of some of the agents which affect 

 testicular function are briefly outlined below. 



1. Internal Factors 



a. Temperature and Anatomical Position of the Testis 



It is well known that in those mammals which have a permanent scrotal 

 residence of the testes failure of the testis or testes to descend properly into 



