2. Endocrines and Populations 267 



rats weighed somewhat less than those of subordinate rats, but the adrenals 

 of the interlopers contained little or no lipid. 



The relationship between social dominance and adrenal activity is, 

 however, not as clear cut as these experiments at first indicate and suggests 

 that a great deal of work needs to be done on the factors which affect 

 dominance-subordinance relationships and w^hat constitutes "social stress" 

 in mammals. The adrenals of the dominant animal in a group do not always 

 weigh the least and occasionally may be the heaviest, even though the 

 average weight of the adrenals of the dominant animals is appreciably less 

 than those of other ranks. Furthermore, the amount of fighting varies 

 greatly from group to group. Finally, the amount of scarring on a mouse in 

 a group is in a general way a measure of its rank. Observation has shown 

 that it is generally safe to assume that the unscarred mouse in a group is 

 the dominant animal, and yet, as we have shown, there is no relationship 

 between the amount of scarring and absolute adrenal weight in groups of 

 albino male mice although there was clearly a tendency for adrenal weight 

 relative to body weight to increase with increased scarring (Christian, 

 1959d) . These results apparently indicate that fighting is a poor measure of 

 social rank and is related only indirectly to it. These results appear to 

 contradict the results of other experiments, although these differences 

 would probably be reconcilable if more detailed information were available 

 on social behavior in these animals. Rather rigid and simple criteria are 

 used to determine rank in animals, such as physical dominance-subordi- 

 nance relationships, and it is quite clear that social interactions are far 

 more complex than this. However, the apparently contradictory results 

 with relation to fighting and dominance in no way invalidate the conclu- 

 sions that purely psychological social pressures are responsible for stimu- 

 lating increased adrenocortical and decreased reproductive activity in 

 groups of mice and rats and that fighting per se has little or no effect on 

 the adrenal hypertrophy observed in groups of animals. One can speculate 

 with some reason that a massive stimulation of the nervous system and 

 adrenal medulla occurs in subordinate animals when they are suddenly 

 confronted with a dominant, aggressive male. Observation shows that 

 these animals are aware of their rank and cower in front of the dominant 

 animal. When there is no escape from constant contact, it seems inevitable 

 that the subordinate animals must suffer from emotional anxiety resulting 

 from a desire to escape from the situation and the inability to do so. Chronic 

 stimulation of the pituitary-adrenocortical system presumably results from 

 the chronic continuation of such a situation. Admittedly this somewhat 

 anthropomorphic interpretation of the situation is largely speculative, but 

 observations of mice in groups inevitably lead one to such a conclusion. 



Finally, Mason (1959) has shown that when rhesus monkeys are kept in 



