500 ANDREW T. RASMUSSEN 



in the human testis. Neither is there any special relation 

 between the blood vessels and the interstitial cells such as 

 was first reported by Boll ('71) as being the typical arrangement 

 in case of the rabbit, but which has not in general been sup- 

 ported by later investigators. When the interstitial cells have 

 enlarged so as to crowd the intertubular space, the capillaries 

 run between the interstitial cells, which of necessity must sur- 

 round the vessels with little or no connective tissue between the 

 capillary wall and the cells. But at other times when the inter- 

 stitial tissue is loose, they are not especially arranged about the 

 vessels. 



DISCUSSION 



In order to get at a single glance the essential points in regard 

 to the question at issue, the principal facts with the authority 

 for the same, has been placed together in the accompanying 

 chart. Occasionally a few incidental facts which are included 

 were not given by the specific authority. Thus the time of 

 hibernation has in some cases been added, as well as other 

 data deemed of interest. Only the approximate time intervals 

 are, of course, possible in such a chart, since these will vary 

 with the seasons and the localities. How.ever, they are be- 

 lieved to be sufficiently accurate to give a proper setting for 

 the various phases of the cycle. The curves are not con- 

 structed upon any quantitative basis, since hot sufficient data 

 are given to make that possible. The highest point of the curve 

 is intended to indicate merely the approximate time when either 

 spermatogenesis or the development of the interstitial cells, 

 as the case may be, is at its highest, according to 'the author's 

 statement of the case. When more than one investigator have 

 reported on the same animal and only slight variations exist in 

 the findings, the curves have been combined into one. Undoubt- 

 edly other observations on seasonal changes in the interstitial 

 cells of adult animals are recorded in the enormous literature 

 upon the testis, but these included in the table are all that Avere 

 found to be directly to the point, after a reasonable search through 

 available sources. 



