HORMONES SI 



scription of the action of any substance on the 

 body. But such is not in reality the case. As 

 Cannon has pointed out, all these facts gather 

 around a central condition of no small biolog- 

 ical interest, namely, preparation for physical 

 struggle. The cessation of abdominal activity 

 and the transfer of blood to the lungs, heart, 

 nervous system, and limbs is an adjustment 

 whereby the nutritive fluids are concentrated 

 in regions important for muscular activity. 

 Increased cardiac vigor improves the circula- 

 tion in these regions. The increase of sugar 

 in the blood adds to its nutritive value for 

 muscular work. The quickened coagulabflity 

 serves as an increased safeguard in case of 

 injury. And the improvement in recovery of 

 muscle from fatigue lengthens the time dur- 

 ing which an animal may continue a struggle. 

 Thus all the changes induced in the body by 

 an increase of adrenalin in the blood may be 

 regarded as emergency measures for times of 

 intense struggle. It is, therefore, entirely 

 natural to find that the extra adrenalin neces- 

 sary for all these changes is produced by the 

 glands whenever the animal is driven into a 

 condition of fear, rage, or pain. These nervous 

 states reflexly excite in the adrenal bodies 



