246 J. J. Christian 



wild mammals. The problem of adrenal hypertrophy with weight changes 

 and the relationship of these changes to the length and severity of the 

 stimulus has been discussed at length by Sayers and Sayers (1949). 



Adrenal weight changes largely reflect changes in the zona fasciculata, 

 which undergoes hyperplasia and hypertrophy following stimulation by 

 ACTH and therefore is indicative of changes in the secretion of glucocorti- 

 coids. Under different circumstances, already discussed, the zona glomeru- 

 losa may hypertrophy, but changes in its size are relatively unimportant 

 with respect to changes in the total weight of the gland because of its rela- 

 tively minor contribution to the total mass of the adrenal. The same state- 

 ment is generally true for the adrenal medulla. Fmally, changes in adrenal 

 weight, when used as an index of cortical activity, should be evaluated in 

 the light of histologic studies, as the amount of lipid in the cells of the 

 fasciculata may vary sufficiently with various functional states to have a 

 marked effect on adrenal weight. For example, stimulation of sufficient 

 intensity to deplete the cortex of visible lipids may result in a decrease in 

 weight whereas activity may actually be greater than in a heavier gland 

 containing a large amount of stored lipid (Christian, 1959b). 



The adrenal medulla in some species may hypertrophy and contribute 

 to changes in adrenal weight. Although the contribution of the medulla to 

 adrenal weight changes is usually negligible, it would be appreciable for the 

 Soricidae, in which the adrenal is composed largely of medulla. Changes in 

 the medulla and cortex of the long-tailed shrews (soricids) have not been 

 studied, although these medullary-cortical relationships have been ob- 

 served in mature individuals of Sorex cinereus, S. dispar, S. fumeus, S. 

 palustris, and Microsorex hoyi. There may be a relationship between body 

 size, adrenocortical mass, and metabolic rate in these minute animals. 



Adrenal weights are useful for field studies, as they may be obtained on 

 fresh or fixed material. From a practical standpoint it is almost essential to 

 obtam adrenal weights from fixed material in mammals the size of mice or 

 smaller, as it is very difficult to clean the glands properly and obtain 

 reliable weights on the fresh glands. Rapid water loss from fresh glands of 

 such small size further complicates the problem. In most circumstances 

 increased adrenal weight is an acceptable indicator of increased adreno- 

 cortical activity, but an effort should be made to obtain the adrenals from 

 suddenly killed specimens, not from captive animals or from those held in a 

 live trap for extended periods, if one wishes to assess adrenocortical func- 

 tion in the animal in its natural state. Animals which have been killed sud- 

 denly are not subject to changes in adrenal weight resulting from capture 

 or handling 



A word of caution is appropriate here with regard to sample size and 

 adrenal weight-body weight relationships. Adrenal weight varies consider- 



