84 MAN AN ADAPTIVE MECHANISM 



respiration was noted, and no corresponding histologic 

 changes were found in the brain, the adrenals or the 

 liver, we assumed that these were pain-free areas, 

 that is, that they contained no contact ceptors. 



In our experiments we found, moreover, that the 

 nature of the response to trauma under ether depended 

 not only upon the location, but also upon the type of 

 the injury. In other words, our investigations showed 

 that the more a given part, by reason of its position, 

 was exposed to injurious contact with environment 

 during the vast periods of evolution, the more thickly 

 is it sown with contact ceptors : and that the more 

 nearly the artificial injuries resembled those prob- 

 ably encountered in the phylogenetic past, the more 

 immediate and vehement was the response elic- 

 ited. Thus, when the skin of any part of the body 

 was burned, cut or torn, there was a prompt rise in 

 blood-pressure, indicating the presence of the many 

 contact ceptors which had been developed to protect 

 the body against the many harmful contacts of like 

 nature which must have assailed the naked body 

 throughout phylogeny. 



As would be expected, the skin of the extremities 

 was found to be more keenly sensitive than that of 

 any other part, for it has been ever by means of its 

 extremities that the animal has first met the mate- 

 rial obstacles in its path. It was by means of con- 

 tact impressions that the organism first distinguished 

 the good from the evil in its environment. Injuries 

 to the paws of an anesthetized dog cutting, crush- 

 ing, fracturing, amputating and burning were at- 

 tended by a sharp rise in blood-pressure, followed by 



