Positive Regulation 



An organism may be so constituted that it reacts to some 

 condition which is favorable, adapting itself so as to obtain 

 benefit from it, even when failure so to react to the condition 

 would cause it no more harm than the loss of an unusual 

 benefit. This form of reaction is sometimes given to a con- 

 dition which the organism does not reach by locomotion, 

 such as a condition which is generally periodic and has no 

 fixed spacial position ( e. g., a weather condition). But if 

 the organism has means of locomotion, the reaction more 

 usually involves a movement toward the favorable condition. 

 This favorable condition may be only occasionally present 

 or it may be only occasionally needed by the organism. The 

 favorable condition to which the organism reacts may be at 

 a distance from, or may impinge upon, the organism. If it 

 is at a distance it must act mediately upon the organism and 

 the organism must have the power of locomotion in order to 

 take advantage of it. The favorable condition may be rela- 

 tively fixed in space, such as air at the top of the water, or 

 it may be relatively fixed in time, such as the regular re- 

 currence of sunlight. To distinguish this form of regulation 

 let us call it positive. 



Positive regulation occurs when some change in the en- 

 vironment or in the physiological state of the organism causes 

 such an adaptive reaction of the organism or such an alteration 

 in the media that the interaction of the newly arranged 

 organism and media which follows brings about increased 

 stability in the organism. In such a process both organisms 

 and media have a double function. The media act first as 

 the stimulus to the organism's adaptive reaction and second 

 as a contributing cause of the increased stability of the 

 organism. The organism likewise must be set or arranged 

 to adjust or orient itself to the changed conditions and also 

 to interact with the novel media so as to cause increased 

 stability in the new relation. The squirrel's storing its food, 



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