THE CONTROL OF LIFE 95 



no reason to think that this cannot be 

 done. Herrmann succeeded in extract- 

 ing a hormone from the corpus luteum of 

 the female guinea pig which on injection 

 stimulated the development of the female 

 characters. The nature of this material 

 is unknown except that it appears to be 

 a lipoid (fatlike) substance but it is, of 

 course, possible that the active substance 

 is quite different and is merely associated 

 with the lipoid. 



The hormone produced by the supra- 

 renal capsules, called adrenalin, has not 

 only been isolated but thoroughly studied. 

 Its chemical structure is known and it 

 has been made artificially. It has an 

 extraordinary effect upon muscle and 

 hence upon the blood vessels, so that it 

 can be used in certain surgical operations 

 (removal of teeth or tonsils) to prevent 

 excessive bleeding. The injection of 

 .00000000125 gram of adrenalin into a 

 frog has a perceptible effect on the rate 

 of bleeding. Cannon states that in 

 higher animals it may be poured out into 



