256 INTRODUCTION TO NEUROLOGY 



canal, adrenalin drives out the blood which, during digestive 

 activity, floods the abdominal viscera. This blood flows all the 

 more rapidly and abundantly through the heart, the lungs, the 

 central nervous system, and the limbs. 



Cannon epitomizes the account from which the above has been 

 condensed in these words: "The emotional reactions above 

 described may each be interpreted, therefore, as making the 

 organism more efficient in the struggle which fear or rage or 

 pain may involve. And that organism which, with the aid of 

 adrenal secretion, best mobilizes its sugar, lessens its muscular 

 fatigue, sends its blood to the vitally important organs, and 

 provides against serious hemorrhage, will stand the best chance 

 of surviving in the struggle for existence." 



The preceding account includes a summary of some of the 

 most securely established facts regarding the peripheral and 

 central nervous mechanisms of painful impressions and the 

 physiology of the emotions, together with a theoretical interpre- 

 tation of the apparently twofold nature of pain as a specific 

 sensation and as a component of the general affective state of the 

 body as a whole. The more general questions concerning the 

 physiological processes related with pleasurable and unpleasant 

 experience and the affective life in general are still more difficult 

 of analysis. It seems probable that pain, unpleasant and 

 pleasurable feelings, emotion, and, in short, the entire affective 

 life are very intimately related on the neurological side. 



Many physiological theories of pleasure-pain have been elaborated, for 

 the most part on very slender observational grounds. It has been suggested 

 that the flexor movements of the body are associated with pain, the extensor 

 movements with pleasure; that constructive metabolism is pleasurable, 

 destructive metabolism disagreeable; that heightened nervous discharge is 

 pleasurable, and the reverse (some form of inhibition or of antagonistic 

 contraction) is unpleasant. Some hold that pain and unpleasantness or 

 disagreeableness are different in degree only, not in kind. Others regard 

 pain as a true sensation, but disagreeableness and pleasure (affective ex- 

 perience) as belonging to a different category which is non-sensory. In the 

 latter case the affective experience may be neurologically related in some 

 way with the various sensations (including pain) or the affective experience 

 and sensations may be independent variables with separate cerebral 

 mechanisms. None of these hypotheses, or many others which might be 

 mentioned, are competent to explain satisfactorily all of the known facts, 

 though strong arguments can be adduced in support of each of them. 



Our own view is that pleasurable and unpleasant experiences are not true 

 sensations, that in the history of the psychogenesis of primitive animals a 



