CHAPTER XIII 



Pain 



THE specific response of pain to stimulation of the 

 contact ceptors has been discussed in Chapter III. 

 There we considered the distribution of pain areas ; 

 the types of contact ceptor stimuli that elicit pain ; the 

 specificity of the pain response to the exciting stimulus ; 

 and the fact that pain is always associated with a pro- 

 tective muscular action. It remains to consider the 

 biologic utility and the mechanism of the pain which is 

 elicited by pathologic conditions. 



Here too the law of phylogenetic association is easily 

 applied, for as response to contact ceptor stimulation is 

 most intense in the parts most commonly subjected 

 to attack and to physical injury, such as the tips 

 of the fingers, the palms of the hands, the soles of the 

 feet, the chest and the abdomen, while the deeply 

 protected portions of the body, such as the liver, spleen, 

 kidneys, brain and lungs are pain-negative, so a type 

 of infection which is associated with pain when it 

 involves one portion of the body may be painless 

 when it involves another portion. Tuberculosis of the 

 lungs, for example, is painless, while intense pain is 

 associated with tuberculosis of the hip. 



I believe it will be found, on careful analysis, that 

 the infections which are associated with pain are those 



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