CHAPTER I 

 THE GENERAL BACKGROUND 



INTRODUCTION 



This study of animal aggregations is concerned with some of the 

 physiological effects of crowding upon the individuals composing the 

 crowd, and is offered as a contribution toward the development of 

 general sociology upon a physiological basis. A few years ago it 

 would have been possible to summarize the knowledge' then existing 

 on the subject with the statement that, except in hibernation or at 

 breeding time, the physiological effects of crowding are uniformly 

 harmful, whether attention is given to the effect upon rate of repro- 

 duction, rate of individual growth, or longevity. Data on these 

 harmful results will be presented later, but they are no longer ac- 

 cepted as a complete picture; in this study they are needed to ob- 

 tain a correct perspective for the recent discoveries of beneficial 

 effects of relatively unorganized crowds of animals. 



Much attention has deservedly been given to the study of or- 

 ganized societies, particularly those of mammals, birds, and insects — 

 sometimes with relation to the light they may throw upon the social 

 relations of man, but frequently on account of their own inherent 

 interest. In the main, consideration of these highly organized social 

 groups falls outside the interests of the present discussion, which will 

 be limited, so far as possible, to the physiological effects of crowding 

 upon organisms whose interrelations have not reached the level of 

 development usually called "social." 



The general physiologists contend with justice that one cannot 

 understand the physiology of man without a knowledge of the gen- 

 eral physiology of all animals and much of that of plants as well. The 

 comparative psychologists conclude similarly that one cannot under- 

 stand the working of the human nervous system without knowing 

 how other nervous systems function. Similarly, an increasing num- 



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