Method of Regulation in Behavior and in Other Fields. 481 



get what we call a positive reaction. The change of behavior is 

 due in each case primarily to the unfavorable stimulation, internal 

 or external. This style of behavior is seen with diagrammatic 

 clearness in the free swimming infusoria. These animals con- 

 tinue their movements as long as they lead to favorable conditions, 

 changing at once such movements as lead away. They thus 

 retain favorable conditions by avoiding unfavorable ones; the 

 positive reaction is seen to be, in a sense, a secondary result of 

 negative ones. 



We have a similar condition of affairs in the taking of food by 

 Amoeba. The animal moves forward with broad front, and 

 comes in contact at a certain point on this front with a food body. 

 Part of its movement is taking it away from the food, part toward 

 the food. On coming in contact, all movement which takes it 

 away is changed, only that being continued which keeps the animal 

 in contact with the food. We have here then the same condition 

 of affairs as in the infusoria — the selection of certain conditions 

 through the rejection of all others. 



This is perhaps the fundamental condition of affairs for organ- 

 isms in general. In higher animals the positive, as well as the 

 negative, reactions, have become complicated through the 

 influences to be brought out later, so that this primitive con- 

 dition is not evident. But the essential point is that unfavorable 

 conditions are rejected as a result of the fact that they produce 

 changes in behavior, and this results in the attainment and reten- 

 tion of favorable conditions. In negative reactions it is the new 

 unfavorable external condition that is rejected, retaining the old 

 favorable internal condition. In positive reactions it is the old 

 unfavorable internal conditions that are rejected, retaining the 

 new favorable external conditions. In both cases the impulse to 

 change of movement comes from interference with the physiological 

 processes — external interference in negative reactions, internal 

 interference in positive reactions. 



To sum up, in the lowest organisms we find individual adjust- 

 ment or regulation on the basis of the three following facts: 



1. Definite internal processes are occurring in organisms. 



2. Interference with these processes causes a change of 

 behavior and varied movements, subjecting the organism to 

 many different conditions. 



3. One of these conditions relieves the interference with the 



