THE GENERATIVE GLANDS 393 



with which the internal secretion of the testicle has up to now 

 been credited. 



This ingenious theory was based, partly upon observations 

 of the cryptorchidic testis, and partly on the results of experiment. 

 In the greater number of instances (man, pig, horse, dog, ram) 

 of cryptorchidic testicle, there is not only malplacement, but also, 

 as histological investigation shows, complete absence of sperma- 

 togenesis ; the cells of Sertoli in the seminiferous tubules are well 

 preserved and the cells of Leydig are more or less developed. 

 That animals with bilateral cryptorchidism are sterile has long 

 been known to breeders, but it is equally well known that such 

 animals possess normal, or even excessive, sexual instinct and 

 that all the male sex characteristics are well marked. The external 

 genitals and supplementary glands are fully developed. Where 

 the cryptorchidism is unilateral, the removal of the normal testicle 

 renders the animal sterile, but it retains its male appearance and 

 habit. The completely castrated stallion is, in Germany, called 

 "Walach," while the bilateral cryptorchis, or the unilateral 

 cryptorchis from which the normal testicle has been removed, is 

 called " Klopfhengst." Cryptorchidic individuals in man in- 

 variably show normal development of the external genitals and 

 male secondary stigmata. 



Later histological investigation (Felizet and Branca, Cunneo 

 and Lecene, Nielsen, Tandler, &c.) confirms the finding that 

 cryptorchidism is invariably associated in both animals and man 

 with suppression of spermatogenesis, defective development of 

 the seminiferous tubules, and apparently normal development of 

 the cells of Leydig. 



Similar changes are produced in the testicular tissue by 

 experimental ligature of the vas deferens. Spermatogenesis 

 ceases; the spermatocytes, and later the spermatogonia?, 

 degenerate and, at the end of a few months, they disappear. There 

 is at first no change in Sertoli 's cells of the seminiferous tubules, 

 and the cells of Leydig retain their morphological integrity. No 

 change is produced, however, in the manifestation of sexual 

 instinct, nor in the development of the secondary signs of sex. 

 Ligature of the vas deferens has frequently been performed by 

 veterinary surgeons in place of castration, but as the animals 

 retained the characteristics of the stallion, the results up to now 

 can hardly be regarded as satisfactory. Similar results have 

 occasionally been observed in cryptorchidic animals from which, 

 in place of the testicle, the enormously developed epididymis was 

 removed. 



According to Shattock and Seligman, ligature of the vas 

 deferens of sheep and poultry does not prevent the development 

 of the secondarv sex characters. 



Further evidence in support of Bouin's theory is supplied by 

 the results of clinical observation. Serious changes in the epidi- 



