68 MAN AN ADAPTIVE MECHANISM 



masses of both the inner and the outer body surfaces 

 are numerous nerve endings, adapted to the reception 

 of specific stimuli. 



These specialized nerve endings are classified as 

 contact, distance and chemical ceptors, according to their 

 distribution and the means by which each elicits its 

 own specific response in the organism. Contact ceptors 

 are distributed throughout the surface layers of skin 

 and mucous membranes and apprehend all bene and 

 nod impulses contributed by direct physical impacts, 

 such as the impacts of stones, dust, debris, external 

 heat and cold, wind and water, food, stings of insects, 

 mechanical injuries and irritations of all sorts. In- 

 cluded among the contact ceptors are the touch ceptors ; 

 the specific ceptors which initiate sneezing, coughing, 

 winking, swallowing, vomiting, hiccoughing, peristalsis, 

 evacuation of the urinary bladder, of the gall bladder 

 and ducts, of the uterus and tubes, of the kidney, of the 

 rectum ; and those ceptors which are concerned in many 

 other protective reflexes throughout the body. Stimu- 

 lation of the contact ceptors results in a quick discharge 

 of energy for local motor acts, and are of special use in 

 guiding the animal away from injurious contacts that 

 threaten his well-being, and toward beneficial contacts 

 that result in nutrition and procreation. Were the 

 animal deprived of his contact ceptors, his vital proc- 

 esses might be carried on by means of his distance and 

 chemical ceptors, but paralysis of the motor acts of 

 ingestion and elimination would soon result in death by 

 starvation, or by poisoning from deleterious unejected 

 waste matter. 



The distance ceptors are concerned principally with 



