192 J- J- Christian 



stimulus and also supply the increased needs of many tissues in order to 

 meet the situation. Selye (1950) introduced the phrase "alarm stimulus" to 

 describe such a stimulus which produces shock and evokes the usual 

 physiologic responses to shock. In the present account an alarm stimulus is 

 defined as any stimulus which, when applied to a mammal, tends to alter 

 fluid and circulatory homeostasis, and therefore necessitates a physiologic 

 adaptive response. This definition is somewhat circular insofar as it is in 

 terms of a response, but it is not restrictive, and it does not imply that the 

 adrenal cortex (at least that part responsible for the secretion of carbo- 

 hydrate-active corticoids) is an essential participant, as is so often assumed. 

 There may be qualitative similarities in the responses to different stimuli, 

 but detailed studies suggest that there are all degrees of variation in the 

 degree of participation of various systems and organs to a gi\'en stimulus. 

 Probably the prime objection to the current concept of "nonspecific" 

 response is the practical one that uncritical usage has tended to obscure 

 important differences in the physiologic responses to different stimuli. 



It should be pointed out that the degree of these responses appears to be 

 relative, as the same responses qualitatively are essential for daily life, but 

 must increase quantitatively in the face of adverse circumstances. A pri- 

 mary function of the endocrine adaptive responses is to insure an adequate 

 circulation with an adequate supply of glucose and oxygen to tissues essen- 

 tial for emergency situations. Part of this function is the maintenance of an 

 adequate circulatory volume and proper electrolyte and fluid balances. 

 These adaptive responses will be discussed in greater detail in the following 

 account. 



II. The Endocrine Glands of Adaptation 

 A. The Adrenal Glands 



1. Introduction 



This discussion is primarily for the benefit of those who are interested in 

 the physiological and comparative aspects of mammalogy. Therefore what 

 is known of the endocrine adaptive mechanisms will be outlined without 

 dwelling on details or becoming involved in the minor details or contro- 

 versies of today's frontiers in endocrinology. 



Research on adaptive mechanisms to a large extent has centered around 

 the adrenal glands, especially the cortex. One of the factors tending to 

 synonomize "stress" with adrenocortical activity has been the measure- 

 ment steroid secretion, weight, ascorbic acid depletion, and cholesterol 



