SEASONAL CHANGES IN INTERSTITIAL CELLS 495 



in the European marmot many of the cells of Leydig are ar- 

 ranged in ceil masses and in cords thus bounded by 'endothe- 

 lium'; but some are also found isolated. Such an arrangement 

 as shown in figure 10 may or may not be present in the case 

 of the woodchuck. The columnar arrangement described by 

 Ganfini ('02) is not found here, though some of the cell groups 

 in the cases just described are somewhat elongated. White- 

 head ('08) does not find this group arrangement typical. In the 

 cat he found columns of cells among the tubuli recti. 



Due to mutual compression, the interstitial cells at this stage 

 vary in shape, with an average diameter in general of 20 ^ to 

 25 11. A few cells may be found that are as small as 14 /x in 

 average diameter. The nucleus is more eccentric and slightly 

 larger, being now 6 ^ to 7 ^ in diameter as compared with 

 about 5 M when the cells are minimal in size. The pigment 

 granules in these ordinary interstitial cells ' have decreased 

 greatly and only now and then is a granule found as may be 

 seen from figure 16. This recalls the findings of Friedmann 

 ('98) who noted that when the interstitial cells of the toad 

 contained much fatty material the pigment was greatly reduced 

 and when the fat disappeared, the pigment was abundant again. 



The dense central mass of cytoplasm is conspicuous and 

 contains a vast number of the fine lipoid granules, some of which 

 are very small (fig. 17). As stated above, these granules are 

 not preserved in Carnoy's fluid and hence 'appear as small 

 vacuoles in the dense central cytoplasm in figure 16 (seen best 

 in the cell marked with a +)• The peripheral cytoplasm is 

 densely packed with the large fatty granules as indicated in 

 figure 18, especially in the insert where three cells are photo- 

 graphed under higher magnification. 



A few of the pigment cells are seen here and there. Some 

 are very much reduced in size and are very irregular in out- 

 line, but others are well preserved. In one case the testis 

 was practically free from pigment either as sma41 granules in 

 the ordinary interstitial cells or as larger spherules filling pigment 

 cells. As a reslilt the testis at this stage is much lighter in 

 color than at any other time. 



