THE EFFECT OF ADRENALIN 177 



the nervous system, and are actually excited to increased 

 activity in times of emotional stress. 



The Effect of Adrenalin on Muscular Power. — 

 It has long been known that a person in time of emer- 

 gency displays unsuspected strength. The familiar phrase 

 " the strength of desperation " refers to this fact. There 

 is some reason to believe that this increased muscular 

 power may be due to the influence of adrenalin in aug- 

 menting the metabolism of the muscles. Since a person 

 in time of stress actually has in his blood more adrenalin 

 than at other times, " the strength of desperation " can be 

 thus explained. 



The Effect of Adrenalin on Basic Metabolism. — 

 Quite recently it has been shown that adrenalin belongs 

 in the group of hormones that regulate basic metabolism. 

 The method of demonstrating this fact is to inject into 

 the veins of a person a small amount of adrenalin and then 

 to measure his resting metabolism. The effect of the in- 

 jection is to increase the metabolism considerably above 

 the normal level. Since no external work is done in basic 

 metabolism, the effect of increasing it by injections of 

 adrenalin is to cause the body to produce more heat than 

 it otherwise would (Chap. VIII). There is also evi- 

 dence that when the amount of adrenalin in the blood is 

 less than normal, as, for example, following injury to the 

 adrenal bodies, the basic metabolism is also less than 

 normal. 



The Relation of Hormones to Racial Character- 

 istics. — Very recently the suggestion has been made 

 that the traits which distinguish one race of human beings 

 from another, and which we call racial characteristics, 

 may be due to a difference in the hormones which the 

 individuals of the different races produce. The import- 

 ance of the suggestion lies in the fact that since racial 

 characteristics are hereditary, being transmitted from 

 parents to children generation after generation, the means 

 of inheritance so far as racial characteristics are con- 



