490 ANDREW T. RASMUSSEN 



internal secretion, since at this time the bodily functions are 

 greatly reduced and metabolism profoundly modified. However, 

 since the internal secretion of the testis has to do with the 

 reproductive side primarily, and not with the vegetative — 

 phases which may be more or less independent — it may not 

 necessarily follow that any marked observable change need be 

 registered in this organ at the beginning of or during this dor- 

 mant state. Certainly the interstitial cells in the woodchuck 

 remain practically unchanged during the hibernating period — ■ 

 December, January, February. In the ground squirrel (Citellus 

 tridecemlineatus) which also hibernates, Mann ('16) reports 

 that the testis, while undergoing definite seasonal variations, 

 does not show any specific change due to the torpid condition. 



At the beginning of March when the animal begins to awaken, 

 the tubules are -ready for a sudden and rapid production of sper- 

 matids and spermatozoa. The woodchuck may be semidormant 

 during this waking up period for several days and even longer. 

 During this sluggish period the changes in the testis commence, 

 so that before the animal has attained what may be termed its 

 homoiothermal temperature, changes in the testis have already 

 occurred. Figures 6 and 7 show these beginning changes in an 

 animal that is just waking up. In the peripheral cytoplasm of 

 the ordinary interstitial cells large fatty globules, which may 

 be blackened with osmic acid, make their appearance and the 

 cells begin to round out. The testis now represents from 

 0.040 per cent to 0.050 per cent of the reduced body weight. 

 However, the animal has lost about one-third of its body weight 

 during the preceding months of inanition, consequently this rela- 

 tive weight of the testis is much exaggerated. 



In the newly awakened and active animal the testis in- 

 creases very rapidly. The interstitial spaces become crowded 

 with enlarging interstitial cells of the ordinary type as is seen in 

 figure 11. In cells which have been fixed in Carnoy's fluid, the 

 cytoplasm is greatly vacuolated (fig. 12) due to the fixer having 

 dissolved the fat. Figure 14 gives an idea of the relative amount 

 of fatty material at this stage. The fat is here blackened with 

 osmic acid. 



