84 B. F. KINGSBURY 



time the cells remain in the interstitial cell state, the amount 

 and rapidity of the follicular degeneration and the size of the 

 ovary, and possibly the type of 'metabolism' are evidently de- 

 termining factors. At one extreme are such ovaries as the rab- 

 bit's, at the other those of mare or cow. 



A brief discussion of the interstitial cells of the testis may be 

 permissible even though no personal work has been done by me 

 on their structure or origin. They appear to be quite abun- 

 dantly present in the fetal testis (numerous papers), less devel- 

 oped during childhood, becoming numerous again at puberty 

 and demonstrable in the active testis, thence forward during life. 

 Their connective tissue origin appears to have been quite clearly 

 shown. Their most striking histological feature is their lipoid 

 and granular content. In histogenetic origin and structure they 

 resemble closely the interstitial cells of the ovary, and like these 

 are connective tissue (stromal) elements which for some causes 

 have undergone the typical hypertrophy and lipoid change. In 

 the testis, however, the analysis of the conditions and relations 

 that underlie the appearance of these cells is far more difficult 

 than in the ovary. In the latter organ the oogenetic growth 

 processes are more distributed in time and place; in the testis, in 

 close proximity are spermatocytes, spermatogonia, spermatids, 

 maturing spermatozoa; and the indifferent or Sertoli cells — com- 

 parable to the ovarian follicle cells — are undergoing their pro- 

 gressive and regressive changes in association with the matura- 

 tion of the male reproductive elements. In the anura, reptiles, 

 birds and mammals this is the case. It is necessary therefore 

 to turn for definite morphological clues to the lower forms, 

 where the processes, progressive and regressive, occur in distinct 

 portions of the organ. Despite the excellent studies of Allen, 

 Whitehead and others I believe that there has not been made 

 a full study of the development of the testis with a view to de- 

 termining the growth correlations that lead to the appearance 

 of the interstitial cells, and such an investigation might add much, 

 even in the complex mammalian testis. That there is such a 

 correlation between the tubule and interstitial cells would ap- 

 pear from the fact that the interstitial cells are not recorded as 



