50 BIOLOGY AND SOCIAL PROBLEMS 



nalin is added, these contractions cease and the 

 bit of intestine relaxes. On the basis of such 

 observations as this, it has been estimated that 

 the adrenalin in our blood is normally about 

 one in two hundred millions. 



Adrenalin has been isolated and is well 

 known chemically. It has in fact been pro- 

 duced synthetically. It is important as a means 

 of checking hemorrhages in minor surgery, for, 

 on local application, it quickly brings about a 

 constriction of the walls of the blood vessels. 



No one knows with certainty what purpose 

 the small, constant amount of adrenalin in the 

 blood serves, but when more of this substance 

 appears, certain profound and significant 

 changes occur. These changes may be stated 

 briefly as follows : a cessation of the activities 

 of the alimentary canal ; a notable shifting of 

 the volume of the blood, from the abdominal 

 organs, to the lungs, heart, central nervous 

 organs, and limbs ; an increased cardiac vigor, 

 an augmentation of the sugar content of the 

 blood ; a hastening of its power to coagulate ; 

 and a rapid recovery of muscle from the con- 

 dition of fatigue. At first sight this seems to 

 be a heterogeneous assembly of physiological 

 effects such as might constitute a formal de- 



