38 THE TESTIS AND ITS RELATION TO REPRODUCTION 



'48). The anterior chamber of the eyeball possesses a temperature much 

 cooler than the internal parts of the body. 



Two types of seminiferous tubules are thus found in mammals. In a few 

 mammalian species (see p. 6) the temperature of the peritoneal cavity is 

 favorable to the well-being of the seminiferous tubule; in most mammalian 

 species, however, a lower temperature is required. On the other hand, the 

 activities of the interstitial tissue of the testis appear to be much less sensitive 

 to the surrounding temperature conditions, and the male sex hormone may 

 be produced when the testes are removed from the scrotum and placed within 

 the peritoneal cavity. 



With regard to the functioning of the testis within the peritoneal cavity 

 of birds it has been suggested that the air sacs may function to lower the 

 temperature around the testis (Cowles and Nordstrom, '46). In the sparrow, 

 Riley ('37) found that mitotic activity in the testis is greatest during the 

 early morning hours when the bird is resting and the body temperature is 

 lower, by 3 or 4" C. 



b. Body Nourishment in Relation to Testicular Function 



The testis is a part of, and therefore dependent upon, the well-being of 

 the body as a whole. However, as observed in the preceding pages the inter- 

 stitial cells and their activities in the production of the male sex hormone 

 are less sensitive to the internal environment of the body than are the seminif- 

 erous tubules. 



The separation of these two phases of testicular function is well demon- 

 strated during starvation and general inanition of the body as a whole. A 

 falling off of sperm production is a definite result of starvation diets, although 

 the germinative cells do not readily lose their ability to proliferate even after 

 prolonged periods of starvation. But the interstitial cells and the cells of 

 Sertoli are not as readily affected by inadequate diets or moderate starvation 

 periods. Sex drive may be maintained in a starving animal, while his ability 

 to produce mature, healthy sperm is lost. On the other hand, long periods 

 of inanition also affect sex hormone production and the sexual interests of 

 the animal. 



Aside from the abundance of food in a well-rounded dietary regime, ade- 

 quate supplies of various vitamins have been shown to be essential. Vitamin 

 Bi is essential to the maintenance of the seminiferous tubules in pigeons. 

 Pronounced degenerative changes in the seminiferous tubules of rats and 

 other mammals occur in the absence of vitamins A and E (Mason, '39). 

 Prolonged absence of vitamin E produces an irreparable injury to the testis 

 of rats; injury produced by vitamin A deficiency is reparable. The B-complex 

 of vitamins seems to be especially important for the maintenance of the 

 accessory reproductive structures, such as the prostate, seminal vesicles, etc. 

 The absence of vitamin C has a general body effect, but does not influence 



