36 



THE TESTIS AND ITS RELATION TO REPRODUCTION 



finement the seminiferous tubules experience marked degenerative changes 

 and only Sertoli cells remain (fig. 19 A, B). The interstitial tissue, however, 

 is not greatly impaired. If such a testis is kept not too long within the abnormal 

 position and once again is returned to the scrotum, spermatogenesis is reju- 

 venated (fig. 20A, B). In a second experiment, the scrotum of a ram was 

 encased loosely with insulating material; a rapid degeneration of the seminif- 

 erous tubules followed. Young ('27, '29) in a third type of experiment found 

 that water 6 to 7° warmer than the body temperature applied to the external 

 aspect of the guinea-pig testis for a 15-minute period evoked degenerative 



Fig. 19. Sections of experimental, cryptorchid, guinea-pig, seminiferous tubules and 

 interstitial tissue. (Modified from C. R. Moore in Sex & Internal Secretions, Williams & 

 Wilkins, Baltimore, 1939.) (A) Testis confined to abdomen for three months. (B) 

 Testis confined to abdomen for six months. Observe degenerate state of seminiferous 

 tubule after six months' confinement. Interstitial tissue not greatly affected by confinement. 



changes with temporary sterility (fig. 21). Recovery, however, is the rule in 

 the latter instance. Summarizing the effects of such experiments involving 

 temperature, Moore (in Allen, Danforth, and Doisy, '39, p. 371) concludes: 

 "The injury developing from applied heat, although more rapidly effective, 

 is entirely similar to that induced by the normal body temperature when the 

 testicle is removed from the scrotum to the abdomen." 



The position of the scrotum and its anatomical structure is such as to 

 enhance its purpose as a regulator of testicular temperature (figs. 2, 6). When 

 the surrounding temperature is cold, the contraction of the dartos muscle 

 tissue of the scrotal skin contracts the scrotum as a whole, while the con- 

 traction of the cremaster muscle loops pulls the testes and the scrotum closer 

 to the body, thus conserving the contained heat. When the surrounding tem- 

 perature is warm, these muscles relax, producing a more pendulous condition 

 to permit heat loss from the scrotal wall. 



