90 MAN AN ADAPTIVE MECHANISM 



which elicits the most powerful response to harmful 

 stimulation of the contact ceptors of the chest and the 

 abdomen. These areas are the ones that respond to 

 tickling by a recapitulation of the combats of our 

 ancestral animal enemies. Undoubtedly, the specific 

 distribution of contact ceptors in the areas which have 

 been the points of attack throughout the ages is another 

 relic of this era of brute contest. The scanty equip- 

 ment of the back and deeper areas with contact cep- 

 tors is evidence that whatever fighting was done, was 

 done face to face and to the death. The silence of the 

 vital organs is the eloquent silence of defeat, bearing 

 testimony to the fatalities of the struggle, as the sensi- 

 tive spots bear testimony to the hazards and escapes. 

 It remains to harmonize certain exceptional occur- 

 rences. We noted experimentally that direct injury 

 to the gall bladder and cystic duct caused no respon- 

 sive rise in blood-pressure. Yet, we know clinically 

 that the passing of gall stones causes great pain. 

 Likewise the experimental cutting and crushing of 

 the kidney was attended with no response indic- 

 ative of the presence of contact ceptors; yet the 

 pain caused by the passing of kidney stones is in- 

 tense. In these instances we have examples of pain 

 as an adaptive response to pressure from within, its 

 purpose being to incite the protective muscular activ- 

 ities of evacuation and expulsion of harmful contents. 

 The same is true of the pain produced in the urinary 

 bladder by pressure, and in the uterus and tubes by a 

 reproduction of the normal type of stimulus which 

 induces the evacuation of their contents. These 

 organs, like the brain, are shielded from external 



