62 The Mechanistic Conception of Life 



to be expected that zoologists and psychologists who lack a 

 physico-chemical training will feel attracted to the subject of 

 tropisms. 



In closing let me add a few remarks concerning the possible 

 application of the investigations of tropisms. 



I believe that the investigation of the conditions which 

 produce tropisms may be of importance for psychiatry. If we 

 can call forth in an animal otherwise indifferent to light by 

 means of an acid a heliotropism which drives it irresistibly into 

 a flame ; if the same thing can be brought about by means of a 

 secretion of the reproductive glands, we have given, I believe, 

 a group of facts, within which the analogies necessary for 

 psychiatry can be called forth experimentally and can be 

 investigated. 



These experiments may also attain a similar value for 

 ethics. The highest manifestation of ethics, namely, the con- 

 dition that human beings are willing to sacrifice their lives for 

 an idea is comprehensible neither from the utilitarian stand- 

 pomt nor from that of the categorical imperative. It might be 

 possible that under the influence of certain ideas chemical 

 changes, for instance, internal secretions within the body, are 

 produced which increase the sensitiveness to certain stimuli to 

 such an unusual degree that such people become slaves to cer- 

 tain stimuli just as the copepods become slaves to the light 

 when carbon dioxide is added to the water. Since Pawlow 

 and his pupils have succeeded in causing the secretion of saliva 

 in the dog by means of optic and acoustic signals, it no longer 

 seems strange to us that what the philosopher terms an ''idea" 

 is a process which can cause chemical changes in the body. 



