PHYSIOLOGY, CHEMISTRY AND PATHOLOGY 441 



In males having a rutting season spermatogenesis occurs only at this 

 time. This periodic activity is usually associated with a great increase 

 in the size of the test is, and in certain forms, most rodents, insectivoria, 

 and hats, with the descent of this organ from the abdomen into the scrotum. 

 According to Marshall, LeCallion and others, a part of this seasonal in- 

 crease in the size of the testis is due to an increased proliferation of the 

 interstitial cells. Watson has shown that the interstitial cells demon- 

 strate a marked development in the non-oestrous periods, and decrease in 

 number as the testis increases in size, while spermatogenesis proceeds. In 

 the hibernating marmot, according to von Hansemann, spermatogenesis 

 ceases and the interstitial cells almost completely disappear. With the 

 assumption of spermatogenesis in the spring the interstitial cells reappear 

 in great numbers. Rasmussen (a) (&) observed that spermatogenesis in 

 the woodchuck progresses slowly during hibernation and then increases 

 suddenly for a month at the termination of this time. This period is now 

 followed by an almost complete absence of spermatogenesis. Following 

 this, spermatogenesis increases again until the following year. The devel- 

 opment of interstitial cells, on the other hand, does not occur except dur- 

 ing the Spring and early Summer. They reach their greatest size only after 

 the Summer and Autumn. 



It appears that all forms of life do not possess interstitial cells in their 

 testes, for, as Pezard has shown, adult Orpington fowls and golden 

 pheasants do not show the presence of these cells even during the period 

 of greatest sexual activity. However, Boring and Pearl state that inter- 

 stitial cells are demonstrable in male chicks just hatched, but not in 

 adults. 



The belief that the interstitial cells formed the internal secretion of 

 the testes was first based upon the finding, by Rienke, of certain crystals 

 in these cells and in the lymphatics of the human testis. These crystals, 

 however, have not been found in other animals. On the other hand, certain 

 experimenters advanced the theory that the generative tissues alone were 

 responsible for the production of the testicular hormone (Nussbaum). In 

 support of this theory is cited the synchronous development of rutting 

 organs with the most rapid production of spermatic cells, It has been 

 further contended that it is the action of the spermatogonia, which at the 

 (breeding season stimulates the production of the rutting organs. Such 

 theories were once justifiable because of the belief that the interstitial cells 

 were trophic elements, whose function it was to take up nourishment from 

 the blood stream and transmit it to the sustentacular cells (Regaud, 

 Plato). 2 



Interstitial Cells and the Testicular Hormone. Many facts demon- 

 strating that the interstitial cells are responsible for the internal secretion 



For an excellent review of the oltfer theories see the paper by Hanes, 1911. 



