184 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Seasonal Changes in Interstitial Cells of Woodchuck.* — A. T. 

 Rasmussen publishes the results of a study of the changes in the 

 interstitial cells of the testis in thirty-five woodchucke {Marmota monax) 

 examined at different seasons of the year. The woodchuck is sexually 

 active only in spring, the female bringing forth a single litter in late 

 April or early May. Hibernation is profound and lasts for four months ; 

 no food is stored up. For purposes of investigation the testes were 

 usually removed from the living animal under ether, but in some cases 

 they were removed immediately after death, and in a few several hours 

 after the animal was shot. During late summer and autumn the 

 interstitial cells of the testis are minimal in size and probably reduced in 

 number. The scanty cytoplasm of these cells contains numerous 

 pigment granules, some fine lipoid granules, but only a few cells contain 

 coarser, more fat-like granules. There are a number of large interstitial 

 cells which are gorged with prominent pigmented granules, and which 

 have resulted from the degeneration of other and more numerous types 

 of interstitial cells. A new spermatogenic cycle is in progress. The 

 testis is small, dark in colour, and abdominal in position. There is no 

 sudden change in the interstitial cells with the onset of hibernation, and 

 little or no change during dormancy, except that there is a slight gradual 

 decrease in pigmentation. Spermatogenesis remains much the same 

 during the torpid state as just before the winter-sleep sets in. The 

 tubules are filled with spermatocytes showing open maturation figures 

 during the entire winter. In the spring, as the animal is waking up, 

 the interstitial cells rapidly enlarge and apparently increase in number. 

 The nucleus increases only slightly. The great increase is primarily in 

 the cytoplasm, and is due to the development of a dense central mass of 

 cytoplasm and the accumulation of fatty globules in the more peripheral 

 portion. Fine lipoid granules are also abundant in the central cytoplasm. 

 The great interstitial cell-development forces apart the tubules and 

 doubles the diameter of the testis, which descends into a pouch essen- 

 tially representing a scrotum, remaining in communication with the 

 abdominal cavity proper. Spermatogenesis suddenly shows renewed 

 activity, and free sperms are seen two or three weeks after the wood- 

 chick has waked up. The interstitial cells do not reach their maximal 

 size till the end of April. There is a distinct decrease in pigmentation. 

 Regressive spermatogenesis begins in late April and a new cycle begins 

 early in May, but the interstitial cells remain well developed for two 

 months longer By July the testes have returned to the abdominal 

 position, the interstitial cells show signs of decreasing, and by August 

 they are little more than naked nuclei. A few cells do not decrease, 

 their lipoid content having been, transformed into pigment granules. 

 The testis as a whole is reduced to about an eighth of its former size, 

 and is darker in colour than at any other stage. Spermatogenesis is 

 slowly progressing uninterruptedly. Interstitial cell-growth seems more 

 uniformly related to the later and regressive stages of spermatogenesis 

 than to the initial stages, but there is evidence of variability even in 

 regard to these. 



• Ann. Journ. Anat., xxii. (.1917) pp. 475-513(3 lis.). 



