2. Endocrines and Populations 265 



others. The remaining mice arrange themselves in some sort of hierarchy in 

 between. It was found that adrenocortical hypertrophy was greatest in the 

 most subordinate animals and was slight or absent in the dominant mice. 

 The adrenals of those in between tended to fall in line in between in a 

 reciprocal relationship to their dominance rank. Fighting cannot have been 

 an important stimulus to mcreased pituitary-adrenocortical activity in 

 these experiments, as the dominant animals fought as much as, or more 

 than, any of the subordinate animals. The mice in these experiments also 

 exhibited changes in the weights of their reproductive organs consistent 

 with suppressed secretion of gonadotropms coincident with increased 

 pituitary-adrenocortical activity. There was no clear-cut decline in the 

 weights of the reproductive organs with decreasing social rank, but the 

 dominant mice had much heavier reproductive organs, especially the pre- 

 putial glands, then the subordinate animals (Davis and Christian, 1957). 

 These results were confirmed and intended in dogs by Eik-nes (1959), who 

 found that the dominant dogs in groups secreted about half the amount 

 of corticoids that the subordinate dogs secreted. Therefore there can be 

 little question that there are significant differences in adrenocortical func- 

 tion associated with differences in social rank. 



In another series of experiments Southwick ( 1959) demonstrated that 

 moving mice into a new environment daily could induce a marked increase 

 in adrenocortical activity as determined by eosinophil counts. That the 

 eosinopenia was not a result of handling was shown by the fact that mice 

 handled in the same way but not placed in a strange situation responded 

 with only a slight fall in circulating eosinophils. The mice transferred to new 

 cages for a period of time every day adapted to the situation, as the eosino- 

 phil count returned to normal levels by the end of the 8-day experimental 

 period. A third series of anunals were placed in groups of four each day and 

 these animals exhibited an 80% mean decline in their eosinophil counts 

 and these counts remained low as long as the animals were placed in groups. 

 Presumably the mice responded to grouping with a marked increase in 

 adrenocortical activity and did not adapt to the situation. It is clear from 

 these results that merely placing mice in a strange situation is an emotional 

 stimulus sufficient to result in a decline in circulating eosinophils and pre- 

 sumably in adrenocortical activity and that grouping constitutes a more 

 profound stimulus to which animals fail to adapt. As we have pointed out 

 previously, it cannot be concluded finally that the eosinopenia was due to 

 increased adrenocortical activity, although it seems likely, imtil increased 

 secretion of epinephrine is ruled out as a causative factor. 



Similar results were obtained when male Norway rats were placed in 

 groups (Barnett, 1955) . The subordinate males, subjected to severe fighting 

 for short periods, at first showed marked decreases in adrenocortical sud- 



