498 ANDREW T. RASMUSSEN 



parently most of them disappear by the end of the next period of 

 hypertrophy. 



The origin of the pigment in the interstitial cells has been 

 debated. Von Hansemann ('95) considered that' it was not due 

 to pigmentary degeneration, but rather that it is an infiltration 

 from some other source, since the pigmented cells are the larger. 

 Kasai ('08), however, states that in the human testis the pig- 

 mented cells are not especially larger and that it is the younger 

 cells that are not pigmented. Pigmentation, according to the 

 latter author, commences in the human testis first at 21 years 

 of age. With the advance of years and especially in old age 

 the pigmentation increases. These facts Kasai took to indicate 

 that it is a pigmentary degeneration — a view fully supported 

 by this work on the woodchuck. Whitehead ('08) believes 

 that the large pigment-laden cells which he observed in a case 

 of cryptorchism are due to pigmentary degeneration of ordinary 

 interstitial cells which in the retained testis have become use- 

 less — there being a normal scrotal testis to supply the necessary 

 internal secretion. 



During this disintegration of the interstitial cells there is a 

 great increase in the number of ordinary adipose cells, which 

 are present in the testis at all times of the year. Fatty degen- 

 eration within the tubules is also seen at this time; in fact, fatty 

 globules are demonstrable in the germinal epithelium at all 

 seasons. 



During all this time spermatogenesis is slowly progressing. 

 The diameter of the tubules changes but little during the entire 

 year. They are probably somewhat smaller later in July, August, 

 and September and larger in November and December. How- 

 ever, the extremes in size may be encountered at other periods of 

 the year and the limited number of animals representing any one 

 period makes a- definite statement impossible. The rather 

 marked variation in the diameter of the tubules included in the 

 general views of the testis in the figures accompanying this paper, 

 is not representative. It happened that in selecting places to 

 show the relative amount of interstitial tissue the tubules were 

 not carefully observed as to size, as was evident from a compari- 



