82 MAN AN ADAPTIVE MECHANISM 



longed pressure on any part of the body produces the 

 pain of anemia which is followed by vigorous muscular 

 activity to hasten the return of the normal circulation. 

 Pain induces the emptying of an overextended urinary 

 bladder, contractions of the large and of the small 

 intestine to overcome obstruction, and delivery from 

 the pregnant uterus. The most exquisite pain re- 

 sults from mechanical irritations of the cornea and 

 is followed by a complicated muscular reaction. 

 Pain of a specific type results from irritation of the 

 pharynx, the larynx or the trachea, and in each case 

 is followed by appropriate muscular reactions. 



Like pain itself, the muscular activity which follows 

 pain is specific in type, location and intensity to the 

 exciting stimulus. That is, the muscular act of cough- 

 ing, which follows the pain produced by an obstruction 

 in the larynx, is specific to the menace in that area. 

 The muscular act of scratching which accompanies the 

 quasi pain of tickling is adequate for an insect's bite, but 

 would be inadequate for the pain produced by intense 

 heat or a heavy blow. 



Pain Areas 



In order to discover the relative distribution of con- 

 tact ceptors in the body and to confirm their adaptive 

 origin, we undertook an extensive research upon ani- 

 mals subjected to various types of trauma, while un- 

 der ether anesthesia. We have stated already that the 

 result of any stimulus is to cause a transformation of 

 potential into kinetic energy for an adaptive reaction ; 

 this adaptive reaction in the case of mechanical injury- 

 being some form of muscular activity tending to protect 



