INTERSTITIAL CELLS OF URODELE TESTIS 233 



tions, such as the intralobular pressure, are likewise altered; 

 profound changes follow. Even before all the spermatozoa have 

 yet left them, the diminution of the intralobular pressure causes 

 the lobules to appear, in cross-section, somewhat less angular 

 .than previously, with the interlobular tissue increased in promi- 

 nence, as is seen in figures 10 and 11. 



The interlobular nuclei present in previous months, compressed 

 greatly by the distention of the lobules, now begin to round out. 

 Numerous transitional forms are seen. The flattened disks 

 become thickened, typical nuclei now being from 18 to 24 /x in 

 diameter and 9 to 12 /x in thickness. These finally are seen as 

 spherical nuclei of from 15 to 18 m in diameter. Figures 26 to 

 30 illustrate stages in this transformation. The cytoplasm 

 increases also as the nucleus rounds out, and fuchsinophile gran- 

 ules and lipoid droplets are soon apparent. These transforming 

 interlobular or stroma cells will henceforth be referred to as 

 interstitial cells, since their succeeding stages leave no doubt as 

 to the correctness of their interpretation as such. It is these 

 cells, doubtless, that Champy has described as forming a ' corpus 

 luteum of the testicle,' since he states that this develops around 

 emptied lobules at the close of the spermatogenetic cycle. 



The increase in quantity of the interlobular tissue is not due 

 entirely to the apparent increase which would result from a 

 shrinkage of the lobule, both in length and diameter, as the 

 spermatozoa being to leave it. Neither is it due entirely to 

 increase in the size of the cells present earlier in the summer. 

 Both the above factors operate to bring to any particular inter- 

 lobular position a greater bulk of tissue. A third factor, however, 

 contributes; I refer to cell division. The flattened nuclei of the 

 July and August period evidently are not under favorable condi- 

 tions for multiplication, as evidence of only one or two mitoses 

 was seen in these months. The study of the interstitial cells 

 of late October was made before any mitoses whatever had been 

 discovered. The great number of cells then present surrounding 

 cross-sections of lobules, as compared with the few widely sepa- 

 rated cells seen earlier, suggested that divisions must occur. 

 (Compare figures 8 and 12.) Search for mitoses among the 



