PHYSIOLOGICAL STATES AS DETERMINING FACTORS. 125 



which must in the long run be classed as injurious, it is thrown into a 

 physiological condition in which its reactions become more rapid and 

 powerful, and of such a nature as to remove the organism from the 

 source of stimulus. We find that in this state the organism reacts to 

 any stimulus to which it reacts at all by a strong negative reaction. 

 In higher animals we frequently find the same condition of affairs, and 

 the animal is then commonly said to be frightened. Finally, we often 

 find in man a similar condition, and here we know certain subjective 

 accompaniments of the physiological condition, the most chai'acteris- 

 tic of which is perhaps the emotion of fear. In all these cases the 

 objective manifestations of the physiological condition are of the same 

 character. Does the fact that in man we know something additional 

 about the matter, the subjective accompaniments, constitute grounds 

 for denying the essential similarity, from a physiological standpoint, 

 of this condition in man and that in the lower organisms? It seems to 

 me that it does not ; in fact, all that is maintained in making the com- 

 parison is that this condition causes similar objective phenomena and 

 is brought about by similar conditions. Further than this our analysis 

 and comparison cannot go. 



Another class of physiological conditions which we can distinguish 

 almost all the way through the animal series is that produced character- 

 istically by intense stimuli, as opposed to faint stimuli. As a rule, any 

 stimulus, even if it is one to which the organisms respond usually by a 

 positive reaction, produces, when it becomes very intense, reactions 

 whose general effect is to remove the organisms from the source of 

 stimulation (negative reactions).* This is true in Amoeba, where weak 

 mechanical stimuli cause spreading out and movement toward the 

 source of stimulus, while strong mechanical stimuli cause it to contract 

 and move away; it is true for Stentor ; it is true for the stimulus of 

 weak and strong light in Euglena and Volvox and many other 

 organisms ; it is true for mechanical and chemical stimuli in the flat- 

 worm ; it is true in general for higher animals and man. In all these 

 cases the intense stimulus evidently changes the physiological con- 

 dition so that the organism now reacts negatively. In man we know 

 that this physiological condition is accompanied subjectively by pain 

 or at least discomfort, and even in higher animals such reactions are 

 usually spoken of as pain reactions. Objectively considered, the 

 phenomena are analogous throughout the animal series, so that we 



* "All organisms behave in two great and opposite ways toward stimulations; 

 they approach them or they recede from them. Creatures which move as a 

 whole move toward some kinds of stimulations, and recede from others. Crea- 

 tures which are fixed in their habitat expand toward certain stimulations, and 

 contract away from others." Baldwin, 1897, p. 199. 



