164 THE PHYSIOLOGY OF REPRODUCTION 



In some animals the renewal of activity in the testes is associated 

 with the descent of these organs from -their position in the abdominal 

 cavity through the inguinal canal and into a cutaneous fold. 1 This 



-.' 



FIG. 50. Diagram illustrating the cycle of phases in spermatogenesis. 

 (From Schafer.) 



.'. S|>erniatogonia (seen dividing at 6) ; a', a", Sertoli cells ; b, spermatocytes 

 (seen dividing at 5) ; <*, spermatids ; *', parts of spermatids which dis- 

 appear when spermatozoa are fully formed ; *, seminal granules. 



1 Berry Hart, "The Nature and Cause of the Physiological Descent of the 

 Teates," / ! not //"/ /'Av*., vol. xliv., 1910. The author sums up the 



essence of tin- process as follows: "The testis is united to a mammary area, 

 at first by the testicular caudal ligament and the inguinal fold or gubernaculum. 

 The developing gubernaculnm, with the aid of the cremaster and peritoneum, 

 forms a pit or fossa for the testis in the Rodentia ; a more complete canal or 

 more or less pendulous scrotum in hi.u'lu-r mammals. By subsequent dis- 

 |ir<>]xirtionate growth of canal and testes, ami finally (according to Frank) by 

 the involution and shrinkage of the gubernaculum, the testes in man become 

 permanently lixli^'d in tin- si-mtiim." Numerous references to literature are 

 appended to this pa}-r. When, as sometimes happens in man, one or both 

 of the testes do not descend or only im)>ri fectly descend, the condition is said 

 to be one of cryptorchism. In eryptordlkb spermatogenesis usually only takes 

 place for a short time after pube'rty (one or two years), if at all, and then the 

 st-minifi'i'iiis tissue degenerates, but the interstitial cells remain. Crew has 

 suggested that the aspermatic state of such testicles is due to the greater 

 temperature within the body as compared with the scrotum, and that the final 

 stages of sperraatogenesis are inhibited by the higher temperature ("A 

 Suggestion as to the Aspermatic Condition, etc." J<mr. <//' .1 i,<it., vol. Ixvi., 1922). 

 Uuyer has made another suggestion, based on his work with spermatotoxic sera 



