The Relation of Adrenal Weight to Body Weight in Mammals

Abstract

For each of 25 sp. of Eutheria (including man) and for 1 sp. (opossum) of Didelphia the log of the combined adrenal wt. in mg. was plotted against the log of body wt. in grams. Only feral animals or active captive animals were used (inactive captive animals show adrenal atrophy). Animals ranged in size from less than 10 g. (masked shrew, big and little brown bats) to over 100,000 (polar bear). The "curve" of the graph is practically a straight line, indicating comparable relative adrenal and body weights as plotted for all species, only those animals below 15 g. showing a small relative decrease in adrenal wt. In those sp. for which there was sufficient data, adrenals of the mature female are relatively heavier than those of the mature male, with the exception of the rabbit. Adrenal and body weights of a series of wild rats (sp. not stated), varying from 20 g. to 800 g., when plotted the same as the other sp., fit the curve perfectly, indicating that the conclusions hold good over a wide age and weight range.