PAIN AND PLEASURE 257 



diffuse unlocalized affective experience of well-being or malaise probably 

 antedated anything so clearly analyzed as a sensation with specific external 

 reference, and that, parallel with the differentiation of true sensations of 

 touch, temperature, and so on in consciousness, pain sensations emerged out 

 of the diffuse affective experience and took their place among the other sense 

 qualities. An essential condition for the appearance in consciousness of a 

 definite sensation like touch or vision is the differentiation in the nervous 

 system of a system of localized tracts and centers related to this function, 

 and in the human body such localized tracts and centers seem to be present 

 for pain. Pain, therefore, considered psychologically and neurologically, is 

 a sensation, and a different neurological mechanism for unpleasantness and 

 pleasantness must be sought. To this problem we shall next turn our 

 attention. 



We have seen above that it is possible to frame a neurological hypothesis 

 which allows a given peripheral sensory neuron to be conceived as trans- 

 mitting, say, a tactual impression from the skin and also a painful im- 

 pression from the same or a different end-organ. Upon reaching the spinal 

 cord the nervous impulses of the tactual series may pass through one type of 

 spinal synapse to the spinal lemniscus, and finally reach the tactual center 

 of the cerebral cortex, and the nervous impulses of the painful series may be 

 drawn off through a second system of synapses for transmission through a 

 distinct system of central pathways. Attention has also been called to the 

 fact that the specific pain nerves and central paths may have been developed 

 by a process of the further differentiation of separate neurons with different 

 peripheral and central connections for these two functions. But what of 

 the pleasurable qualities which seem similarly to be associated with some 

 sensory impulses? 



The simplest view seems to the writer to be that the normal activity of 

 the body within physiological limits is intrinsically pleasurable, so far as it 

 comes into consciousness at all. There is a simple joy of living for its own 

 sake, and the more productive the life is, within well-defined physiological 

 limits of fatigue, good health, and diversified types of reaction, the greater 

 the happiness. The expenditure of energy within these physiological limits 

 is pleasurable per se except in so far as various psychological factors enter to 

 disturb the simple natural physiological expression of bodily activity. Such 

 disturbing factors are anxiety, want, rebellion against compulsory service, 

 and unrelieved routine. The expenditure of intelligently directed nervous 

 energy along lines of fruitful endeavor is probably the highest type of 

 pleasure known to mankind. 



But it should be borne in mind that the normal activities of the body are 

 all combined into adaptive systems, that is, they are directed toward the 

 accomplishment of definite ends and not directed at random. Even in 

 instinctive activities of the invariable or innate type, though there may be no 

 consciousness of the end to be attained, the actions are not satisfying to the 

 animal unless they follow in the predetermined adaptive sequence (p. 61). 

 The play of both men and other animals is likewise always correlated around 

 some definite physiological motive. And it is even more conspicuously true 

 that the intelligently directed activities are unsatisfying unless they attain, 

 or at least approximate to, some particular end. Stated in other words, it is 

 not the activity which is pleasurable, so much as the accomplishment, or, in 

 the case of delayed reactions, the hope of accomplishment. 



The normal discharge, then, of definitely elaborated nervous circuits 

 resulting in free unrestrained activity is pleasurable, in so far as the reaction 



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