Receptors, Neurons, and Effectors 127 



so that a more or less permanent habit may be formed by one perform- 

 ance. 2 ' 



THE INTERRELATIONS OF REFLEXES AND CONSCIOUSNESS. 



The connection between " mind " and " body " has long been a sub- 

 ject of dispute. Several theories have been advanced, of which the 

 " interaction theory " and the " parallel theory " are the most conspicuous. 

 According to the first, the " mind " influences the " body " causally, and 

 vice versa. According to the second, neither can have any causal effect 

 on the other, but processes in both go on harmoniously, as in two clocks 

 keeping the same time. 



The usual discussions of the interrelation of " mind " and " body " are 

 not enlightening, because of the vague meanings of the two terms (" mind " 

 and " body " ) . The parallelists are in most cases discussing the relation 

 between perceptible objects and matter (i. e. the atoms, electrons, or 

 whatever other symbols are used to describe the objects and phenomena 

 perceived). The interactionists, on the other hand, are usually more 

 concerned with the relation between the perception of objects and the 

 objects perceived, and the relation between objects of internal sense and 

 objects of external senses. The two theories (of interaction and of 

 parallelism) are really not contradictory, but are supplementary to each 

 other. 



We cannot say that neuro-muscular processes cause consciousness, any 

 more than we can say that conscious processes cause the nerves and 

 muscles. We may however say that neuro-muscular processes cause con- 

 scious processes (i. e., changes in consciousness). On account of the 

 vagueness of the term " cause ", it is preferable to express this relation 

 by saying that neuro-muscular processes condition consciousness, mean- 

 ing thereby, that the sequence of changes in consciousness is, in part 

 at least, dependent on and directed by the sequence of change in neuro- 



27 The mechanism by which the pleasurable reaction fixes a habit, when the circular 

 reflex is not involved, is a matter for conjecture. The most plausible conjecture is 

 that the fixing of the arc, i. e., such action upon the series of synaptically connected 

 neurons as makes the arc the most probable route of discharge upon repetition of the 

 stimulus, is the work of a hormone liberated by the pleasurable reaction. This hor- 

 mone may conceivably be furnished by the pituitary body; and if we assume that the 

 last arc formed is the most sensitive to fixation, by reason of the progressive disap- 

 pearance of the effects of the discharge current, we have a scheme which may explain 

 several difficult points. For example, this theory explains why, although one may 

 make a number of " wrong " reactions in the attempt to open a puzzle box, the final 

 " right " action is retained. 



This is merely a working hypothesis, which offers opportunity for experimental 

 work, and has not been suggested before, so far as the author is aware. 



