increased margin of stability which is insurance against 

 future dangers and permits the organism some rest from 

 the activities of negative regulation. The two forms of 

 regulation are combined in the food reaction of most an- 

 imals. Hunger results in migratory search after food as 

 well as in its capture. Many animals, however, capture 

 food for future use when the conditions of negative regu- 

 lation are not present. The two forms of regulation are, 

 for instance, combined when a man rises in the morning partly 

 because he is no longer comfortable in bed and partly be- 

 cause he hears the water running into his tub. 



The direct interaction between the conditions existing 

 at any given time as well as the resulting adaptations in the 

 manifold may be described as follows: 



In negative regulation unfavorable media (present or 

 at a distance) may cause a change in the organism that 

 makes it either resist such media, or avoid or migrate from 

 such media, or analyze or synthesize such media into in- 

 nocuous or favorable media. Or some unfavorable part or 

 process in the organism may cause its own elimination or 

 discontinuance, either by interaction with the media, or by 

 action within the organism, or by both of these. 



In positive regulation favorable media (present or at 

 a distance) may cause a change in the organism that makes 

 it either interact with such media or enter into or migrate to 

 such media. Or innocuous media (present or at a distance) 

 may cause a change in the organism that makes it analyze or 

 synthesize such media into favorable media. Or some favor- 

 able part or process in the organism may cause its own main- 

 tenance or continuance, either by interaction with the media 

 or by action within the organism or by both of these. 



[EIGHT 



