244 /. /. Christian 



long-term physiologic reactions which may have widespread effects on the 

 host (Elmadjian ct at., 1958; Ratcliffe and Cronin, 1958; Christian, 1959b; 

 Mason, 1959) . Close confinement, for example, can result in atrophy of the 

 adaptive mechanisms with a resultant marked susceptibility to any subse- 

 quent alarming stimulus (Christian and Ratcliffe, 1952). Social competi- 

 tion, social pressure, or chronic anxiety have been shown to produce marked 

 physiologic responses (Christian, 1959a; Mason, 1959) Emotional factors, 

 of necessity, have their begmning in the central nervous system as a result 

 of sensory stimuli received from the external environment via the visual, 

 aural, and olfactory sensory receptors. Therefore they are part of the com- 

 plex system responsible for integrating the mammal with its immediate 

 environment. 



Whatever the particular adverse stimulus may be and regardless of the 

 pathway of its reception by the animal, whether sensory, traumatic, or 

 otherwise, all stimuli have the ability to produce shock and evoke physio- 

 logic adaptive responses in the mammal. Shock is a vaguely defined entity, 

 and there is no general agreement with regard to its exact nature or cause 

 (see Selye, 1950; Scudder, 1952; Bing, 1952; Zweifach, 1952; Engel, 1952; 

 Agate, 1952; Randall, 1952). Moreover, its primary effects and the re- 

 sponses to it are often difficult to separate. Fundamentally the principal 

 manifestations of shock involve changes in the circulatory system leading 

 to inadequate circulatory function and eventually circulatory collapse. If 

 one keeps in mind that the fundamental changes seem to be blood sludging 

 (Knisely et at., 1947), changes in selective permeability of the peripheral 

 vascular bed (Zweifach, 1952), capillary and arteriolar atony and hypo- 

 reaction of the vascular musculature to epinephrine and even direct stimu- 

 lation with a resultant visceral vasodilatation (Zweifach, 1952), then the 

 secondary effects of hemoconcentration, hypotension, fall in blood volume, 

 decreased cardiac output, and increased hematocrit are more easily under- 

 stood. In general shock seems to involve a generalized failure of circulatory 

 integrity. With a superimposed relative circulatory stasis and hypoxia, 

 these alterations became more profound and the whole process becomes a 

 vicious circle (Zweifach, 1952) . It is not known by what specific means 

 these alterations in circulation are effected, but that they involve both 

 neural and humoral components can hardly be questioned. We have re- 

 peatedly emphasized that the basic role of the adaptive reactions is to 

 maintain vascular integrity in opposition to forces tending to destroy it as 

 well as to prepare the organism to meet emergency situations. Most 

 alarming stimuli also produce an immediate discharge of the medullary 

 hormones epinephrine and norepinephrine with mobilization of glucose 

 reserves, increased heart rate and strength of beat increasing cardiac out- 

 put, and constriction of visceral and cutaneous blood vessels with a re- 



