II 



THE SIGNIFICANCE OF TROPISMS FOR PSYCHOLOGY^ 



I 



A mechanistic conception of life is not complete unless it 

 includes a physico-chemical explanation of psychic phenomena. 

 Some authors hold that even if a complete physico-chemical 

 analysis of these phenomena were possible today it would leave 

 the "truly psychical" imexplained. We do not need to enter 

 into a discussion of such an objection since we are still too far 

 from the goal. We are at least able to show for a limited group 

 of animal reactions that they can be explained imequivocally on 

 a purely physico-chemical basis, namely, phenomena which the 

 metaphysician would classify under the term of animal "will." 



Through the writings of Schopenhauer and E. von Hart- 

 maim I became interested in the problem of will. When as a 

 student I read Mimk's investigations on the cerebral cortex 

 I believed that they might serve as a starting-point for an 

 experimental analysis of will. Mimk stated that he had 

 succeeded in proving that every memory image in a dog's 

 brain is localized in a particular cell or group of cells and that 

 any one of these memory images can be extirpated at desire. 

 Five years of experiments with extirpations in the cerebral 

 cortex proved to me without doubt that Munk had become the 

 victim of an error and that the method of cerebral operations 

 may give data concerning the path of nerves in the central 

 nervous system but that it teaches little about the dynamics of 

 brain processes. 



A better opportunity seemed to offer itself in the study 

 of the comparative psychology of the lower animals in which 



1 Lecture delivered at the Sixth International Psychological Congress at 

 Geneva, 1909. (After a translation in Popular Science Monthly by Miss Grace B. 

 Watkinson.) Reprinted by courtesy of Professor James McKeen Gattell. 



35 



