HORMONES 61 



operations, we know that within a certain 

 range, we can alter them to suit our will. 

 They may be hastened, or slowed, or stopped 

 altogether, though not indefinitely; in other 

 words, they are more or less voluntary. The 

 respiratory movements then include not only 

 hormone control, but reflexes of the simplest 

 class and willed actions, a range which, as I 

 intimated before, involves almost every form 

 of control known in the body. 



The fact that hormone action is often com- 

 bined with nerve action brings us face to 

 face with the ancient doctrine of the humors. 

 These were supposed to determine personality 

 in a way already indicated. Many substances 

 produced in the body, though not specifically 

 hormones, may affect our cerebral cortex in 

 such a manner as to color our whole lives, in 

 fact determine our temperaments. We all rec- 

 ognize the passing effect of tea, coffee, or al- 

 cohol. When these materials are not taken in 

 sufficient quantities to prove poisonous, they 

 serve as intellectual alteratives, and the tem- 

 porary condition called forth by them leads 

 us to suspect that the naturally vivacious or 

 taciturn person may have within him a spring 

 that generates unceasingly the appropriate 



