106 THE POPULAR SCIENCE MONTHLY 



it gives for the application of the law of mass action (and other physico- 

 chemical laws) to phenomena which usually form the material for 

 psychological speculation. To make possible a better understanding of 

 my lecture, let me mention briefly how I came to hold the views set 

 forth here. 



The writings of the metaphysicians on the will in nature led me to 

 an experimental analysis of the nature of will. When in my first years 

 at the university Munk's investigations on the cerebral cortex fell into 

 my hands I believed that here was a starting point toward my goal. 

 Munk 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 will. 

 Five years of experiments later 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 can really give only 

 data concerning the nerve connections in the central nervous system 

 but teach practically nothing about the dynamics of brain processes. 



A better way seemed to lie in the comparative psychology of the 

 lower animals in which the memory apparatus is developed but slightly 

 or not at all. It seemed to me that some day it must become possible 

 to trace the apparently random movements of animals back to general 

 laws, just as definitely as it has been done for the movements of the 

 planets, and that the word " animal will " is only the expression 

 of our ignorance of the forces which prescribe for animals the direc- 

 tion of their apparently spontaneous movements just as unequivocally 

 as gravity prescribes the movements of the planets. For if a savage 

 could directly observe the movement of the planets and should begin 

 to ponder over it, he would probably come to the conclusion that a 

 " will action " guides the movements of the planets, just as a chance 

 observer is inclined to assume that " will " causes animals to move in a 

 given direction. 



The scientific solution of the problem of will seemed to consist in 

 finding the forces which unequivocally determine the movements of 

 animals, and in discovering the laws according to which these forces 

 act. Experimentally, the solution of the problem of will must take the 

 form of forcing, by external means, any number of individuals of a 

 given kind of animal to move in a definite direction by means of their 

 locomotor apparatus. Only if this succeeds have we the right to 

 assume that we know the force which under certain conditions seems 

 to a layman to be the will of the animal. But if only a part of the 

 number moves in this definite direction and another does not, then we 

 have not succeeded in finding the force which in a given case deter- 

 mines unequivocally the direction of movement. 



One other point should be observed. If a sparrow flies down from 



