490 H. S. 'Jennings. 



physiological processes are not stereotyped in character, but 

 varied. Under violent injurious stimulation respiration may 

 become for a time rapid, then is almost suspended. The heart 

 for a time beats furiously, then feebly, and there is similar varia- 

 tion in other internal symptoms. 



Thus it seems clear that interference with the life processes 

 does induce varied activities in other ways than in bodily move- 

 ments, and that among these are varied chemical processes. 

 There is then presented opportunity for regulation to occur in 

 the same way as in behavior. Certain of the processes occurring 

 relieve the disturbance of the physiological functions. There 

 results then a cessation of the changes. In other words, a certain 

 process or condition is selected through the fact that it does relieve. 



There is much evidence that the law of the readier resolution of 

 physiological states after repetition applies to other bodily pro- 

 cesses as well as to behavior. The much readier induction of 

 digestive trouble by a small quantity of a certain food, after a 

 large quantity has once induced it is perhaps an example; many 

 better ones are given by Semon ('05). If the analogy with 

 behavior holds in this respect, there will be present at a later 

 period certain fixed methods of chemical response, by which the 

 organism reacts to certain sorts of stimulation — as by the pro- 

 duction of a definite antitoxin when a certain poison is introduced. 

 Definite organs or organisms will have left open to them only 

 certain limited possibilities of variation — due to the development 

 of something corresponding to the "action system" in behavior. 

 Thus, in the pancreas there will not exist unlimited possibilities 

 as to the chemical changes that may easily occur. Its "action 

 system" will be limited perhaps to the production of varied 

 quantities of certain enzyms — amylopsin, trypsin, etc. The 

 proper selection of these few possibilities will then occur by the 

 general method sketched. When digestion is disturbed by food 

 that is not well digested, variations in the production of the 

 different enzyms will be set in train, and one of these will in time 

 relieve the difficulty, through the more complete digestion of the 

 food. Thereupon the variations will cease, since their cause has 

 disappeared. By still more complete fixation of the chemical 

 response, through the law of the readier resolution of physiological 

 states after repetition, an organ or organism may largely lose 

 its power of varying its chemical behavior, and thus be unable to 



