INTERSTITIAL CELLS OF URODELE TESTIS 215 



Bell ('16), on the other hand, is emphatic in the statement of his 

 belief that the interstitial cells cannot be responsible for secondary 

 sex characters, as he finds these cells developed '4n the testes of 

 tubular partial hermaphrodites with feminine secondary sex 

 characters .... to a degree that is rarely seen in the 

 undescended testis and never in the normal testis;" Boring and 

 Pearl ('18) conclude from their study of hermaphrodite fowls 

 that ''interstitial cells are clearly shown to have nothing to do 

 with any of the secondary sex characters." 



Considerable attention has been given to the embryonic 

 development of these cells, as w^ell as to the periods at which, 

 in the life of the individual, their maximal development is at- 

 tained. Their prominence in human embryos and their rel- 

 atively smaller bulk in the eight-year-old boy were noted by 

 Hofmeister ('72). Kasai ('08), in a very complete series of 130 

 human testes, found that the increase in the interstitial cells 

 which occurs at puberty is followed by an apparent decrease; 

 the reduced number peculiar to the period of sexual activity is 

 then followed by an increased number during old age. Such a 

 condition is difficult of explanation if one assumes the responsi- 

 bility of these cells for the development of sex characters or 

 instincts; neither is the complete disappearance of these cells 

 in adult male fowls, as reported by Boring and Pearl ('17), and 

 confirmed by Nonidez ('20), in accord with such an assumption. 



CYCLIC CHANGES 



Historical 



The cyclic changes of the cells in animals which mate only 

 at widely separated periods have recently attracted the attention 

 of investigators. Studies have been undertaken to determine 

 in what relation their maximal development stands to the periods 

 of the sexual or spermatogenetic cycle; a constant relation, if 

 established, might serve as evidence of the production of an 

 internal secretion or give a clue to its possible influences. These 

 investigations are here briefly reviewed in order that the varying 

 results thereof may be more clearly brought before the reader. 



