58 THE SOCIAL LIFE OF ANIMALS 



oxygen than if two or more share the same amount 

 of liquid. By one device or another, grouping fre- 

 quently decreases the rate of respiration. Several of 

 these devices are known to us. Professor Child 

 showed many years ago (31) that when animals are 

 exposed to a strongly toxic material, those with the 

 higher rate of respiration, though otherwise similar, 

 die first. This has been applied to group biology by 

 direct tests, and it has been shown that the group, 

 by decreasing the rate of oxygen consumption of its 

 members, makes them more resistant to the action 

 of relatively strong concentrations of toxic materials. 



Perhaps I have said enough to show that under 

 a variety of conditions groups of animals may be 

 able to live when isolated individuals would be 

 killed or at least more severely injured by unaccus- 

 tomed toxic, chemical elements, strange to their nor- 

 mal environment. 



Will the same relationship hold in the presence 

 of changes in physical conditions? There is a con- 

 siderable and growing lot of evidence that massed 

 animals, even those that can be called cold-blooded, 

 are harder to kill by temperature changes than are 

 similar forms when isolated. (51, 126) This interests 

 us because massing of such animals at the onset of 

 hibernation was recognized as one of the early ex- 



