IL 11. Whitehead 11)7 



of Phito, that the function of Leydig's cells is to store up fat and pass 

 it on through the walls of the tubules to be used as pabulum in sper- 

 matogenesis, the evidence is negative. The Leydig's cells of the pig's 

 testis contain little or no fat, while the tubules show large quantities of 

 that substance; nor could 1 detect the minute canals described by him in 

 the walls of the tubules. Moreover, if recent investigations upon fat 

 metabolism are to be accepted, fat entering the tubules from the outside 

 would probably pass through their walls, not as such, but rather as its 

 two liquid components. Some support, however, might be derived for 

 an extension of Plato's theory as suggested by v. Lenhossek, according to 

 which the function of the interstitial cells is to store up, not merely fat, 

 but other material as well, to be used as pabulum by the tubules. The 

 most important facts in the development of Leydig's cells, it seems to me, 

 are the alternating periods of hypertrophy and atrophy, and the struc- 

 tural characters of these cells during the stage of hypertrophy. The 

 periods of hypertrophy precede, while those of atrophy are synchronous 

 with, periods of rapid growth by the seminal tubules. Moreover the 

 changes in the interstitial cells, though occupying much more time, are 

 comparable, to some extent, with those which occur in secreting cells. 

 So that the appearances described might be interpreted as possibly in- 

 dicating that the Leydig's cells elaborate a specific pabulum for the 

 tubules during the development of the testis. 



I wish here to thank Professor F. P. Mall for the courtesy of a seat 

 in his laboratory while this article was in preparation. 



