§ 3 



REACTION TO STEROID HORMONES 



15 



characteristic of male hormones. The characteristics of this 

 curves are:— 



Latent period, i hour. Linear growth, during the first 

 phase, lasts at least 5 >4 hours. 



pregnanedic! 



10 12 



hours 



2 4 6 6 



Fig. 16. Ovipositor growth curves after administration of pregnanediol. 



It is interesting to consider more closely the relation 

 between the biological activity and the chemical constitution 

 of the 9 substances mentioned above. 



We shall define the most active hormone as that of which, 

 irrespective of the duration of the latent period, the smallest 

 quantity per unit of time produces the greatest initial growth 

 of the ovipositor. The activity may then be further defined 

 as the amount of growth per hour caused by i 7 of hormone 

 per 750 ml water at 22° C, providing that the hormonal 

 concentration does not change significantly after the reaction 

 ceases. 



In the case of pregnenes, pregnanes, and allo-pregnanes, the 

 diones are always more active than the olones. In their turn 

 the olones are always more active than the dioles. 



It further appears that, of the diones, A 4,5-pregnene is 

 nearly 4 times as active as A 5,6-pregnene, and allo-pregnane 

 9 times as active as pregnane. 



Of the olones, allo-pregnane is 14 times as active as preg- 

 nane, and nearly i ^ times as active as A 5,6-pregnene. 



Of the dioles, allo-pregnane is 36 times as active as 

 pregnane. 



The activity of the allo-pregnanes evidently depends on 

 the number of = O-groups. When one = O is replaced by 

 one -OH, activity is weakened 8 times. When a second = O 

 is replaced by -OH, there is again a 4- fold weakening. 



The activity of the pregnanes appears to be dependent on 



