4O LEO LOEB. 



or underdevelopment of the tubules has been observed, or pro- 

 duced experimentally (ligation of vas deferens, Roentgen ray 

 injury of the testicle (4) (5) and certain diseases) a hypertrophy 

 or a hyperplastic condition of the interstitial gland has been 

 noted. Herxheimer and Hoffman (5) suggest that this hyper- 

 plasia is comparable to the substitutive growth of connective 

 tissue which takes place whenever parenchymatous elements are 

 destroyed. This explanation, however, does not seem to take 

 into account the principal variations which have been observed 

 in the condition of the interstitial gland. Bouin and Ancel (i) 

 have shown that in the horse the interstitial gland is present in 

 the fetus ; it degenerates in the immature animal and begins anew 

 to develop at the time of puberty. In the sexually mature animal 

 there seems to exist a certain antagonism between the activity of 

 the seminiferous tubules and the interstitial gland. The inter- 

 stitial gland becomes hyperplastic in cases in which the tubules 

 decrease in activity and vice versa. Under the conditions of 

 tubular atrophy or degeneration which we named above the 

 interstitial gland hypertrophies, and according to Tandler and 

 Grosz in the mole, in which sexual activity follows a yearly cycle, 

 the interstitial gland shows the greatest development at a time 

 when the seminiferous tubules are least active. In hibernating 

 animals the interstitial gland decreases at the period of general 

 metabolic inactivity (von Hansemann) ; similarly in cases of very 

 pronounced general undernourishment, or of very marked degen- 

 erative processes in the testicle the interstitial gland suffers and 

 may disappear. Some observations indicate, furthermore, that 

 under certain conditions extirpation of one testicle may lead to a 

 hypertrophy of the interstitial gland in the second one. All 

 these facts can evidently not be explained otherwise than by 

 assuming that there are several factors active and that chemical 

 and not merely mechanical substitutive factors play a role in the 

 regulation of the growth of the interstitial gland. It seems to be a 

 general function of gland and other epithelial cells to stimulate 

 through their activity the surrounding stroma. We have de- 

 scribed such an occurrence especially in connection with the 

 cyclic growth of the mammary gland, but 'it seems to be a phe- 

 nomenon of general significance. In a similar way we may as- 



