92 MAN AN ADAPTIVE MECHANISM 



of the palms of the hands, the tips of the fingers, the 

 soles of the feet, the surfaces of the chest and abdomen, 

 which have ever borne the brunt of attack, are thickly 

 sown with protective mechanisms. Thus contact cep- 

 tors are more thickly sown upon the outer surface of the 

 body, as compared with the inner, the front as com- 

 pared with the back, the extremities as compared with 

 the trunk. 



We see that the contact ceptors respond to stimula- 

 tion by all agencies which have exerted a powerful 

 influence for life or death upon the species in the past, 

 while they do not respond to such equally fatal, but 

 lately developed, artificial agents as electrical currents, 

 rifle bullets, keen-bladed knives, radium emanations 

 and the X-ray. Had these agencies been factors in 

 the environment throughout phylogeny, those species 

 incapable of evolving mechanisms of defense, either 

 of structural or functional character, would long since 

 have been eliminated, as have been those in which 

 there was evolved no means of defense against sun 

 and wind, against insects and microorganisms, against 

 poisons and deleterious food. As the harmful effects 

 of any environmental agent, without awakening any 

 neuro-muscular response, may injure or destroy other 

 parts of the body than those exposed to their impinge- 

 ment throughout phylogeny, so these newly developed 

 agents can injure the whole body without pain. A 

 device of exquisitely sharp knives driven at a super- 

 latively high speed might cut the body to pieces with- 

 out exciting any neuro-muscular response. 



In the absence, as in the presence, of these adaptive 

 mechanisms, therefore, we are offered a rich glossary for 



