150 BIOLOGICAL ASPECTS OF HUMAN PROBLEMS 



individual poisons and of their specific effects is 

 still meager, owing to the great technical difficulties 

 that surround the investigation of these substances. 

 But of the truth of the following statement there is 

 no question. There are many conditions of slight or 

 considerable mental disturbance in which irritability, 

 depression, or confusion of thought is due to intoxi- 

 cation of the brain from intestinal poisons, and in 

 these cases there is a rapid return to a normal state 

 when this intoxication ceases. The suffering caused 

 by such poisonings is real and great. It affects not 

 merely the happiness of the subject of the intoxica- 

 tion, but, through its influence on conduct, his asso- 

 ciates are also implicated. When temperamental 

 peculiarities exist, they may be greatly exaggerated 

 by a state of intoxication and produce distinctly 

 regrettable results. And one of the most unfortu- 

 nate features of these poisonings, especially when 

 they are established, is that their true nature is 

 commonly not recognized, so that a disorder is per- 

 mitted to persist which might be mitigated if met in 

 timely fashion. 



Let us turn now to the hundred avenues of direct 

 approach to the brain by the nerves that focus there 

 from all parts of the body. If we consider, even 

 casually, the great sensory pathways to the brain, 

 we cannot fail to be impressed by the opportunities 

 that normally exist for the most varied stimuli to 

 register themselves in the cerebral hemispheres. 

 The chief of these stimuli come through the skin, the 



