SECONDARY SEXUAL CHARACTERS. 4! 



sume that growth processes in the seminiferous tubules stimulate 

 the activity of the connective tissue cells and those specialized 

 connective tissue cells which have the potentiality of becoming 

 transformed into interstitial gland. This would explain the 

 development of the interstitial gland during embryonic develop- 

 ment and at the time of puberty. We might designate this as 

 the concomitant growth of the interstitial gland. In order to 

 explain the second kind of growth in the interstitial gland, 

 which we might call the "alternative growth," we must assume 

 that in a certain way the activity of the sexually active seminif- 

 erous tubules exerts an inhibiting effect on the growth of the 

 interstitial gland and that a diminution of this inhibiting effect 

 leads to the "alternative" growth of the interstitial gland. An 

 analogous condition is found in the rabbit ovary in which the 

 atresia of certain follicles leads to a secondary gland-like develop- 

 ment of the theca interna. How far such an equilibrized con- 

 dition is maintained through chemical, how far through finely 

 adjusted mechanical factors, we do not know at present. How- 

 ever, in the somewhat analogous case of the transformation of the 

 connective tissue cells of the uterine mucosa into decidua, we 

 have analyzed the underlying factors experimentally and found 

 that a combination of specific chemical and mechanical factors, 

 which latter are likewise to a certain extent specific, is responsible 

 for this change (6). 



In addition, the interstitial cells of the testicle are accessible 

 to that chemical stimulation which is implied in compensatory 

 hypertrophy and they are furthermore affected by lack of com- 

 mon foodstuffs. 



2. The specific effects exerted by the interstitial cells have 

 been ascribed by Bourn and Ancel to certain products formed 

 within the cells which microchemically behave like fats or lipoids. 

 We found, in our case, reasons for assuming that drop-like sub- 

 stances were furnished the interstitial cells from the surrounding 

 lymphatics and perhaps also from the blood capillaries. How 

 far the substances taken up from the circulation and perhaps 

 modified within the cells are identical with the substances de- 

 scribed by Bouin and Ancel and Whitehead, we cannot at present 

 decide. 



