THE CONQUEST OF DISEASE 



cut off, if the skinning process is begun at once, 

 the animal will kick hard enough to break the 

 knacker's arm. I have seen a dog with the 

 spinal-cord divided make spasmodic move- 

 ments of his hinder extremities and heard a by- 

 stander comment upon the evidence of suffer- 

 ing, when the movements were in no wise 

 struggles prompted by pain. The person, ig- 

 norant of the physiology of the nervous system, 

 thinks of a struggling animal as a suffering 

 animal, not recalling to mind the struggles of a 

 chicken with its head cut off. Pain is a psychic 

 phenomenon, and lower men and animals have 

 but little appreciation of it. 



Operations Another point worthy of consideration in 



painless. this connection is the painlessness of most oper- 

 ations even upon man. Physical pain is 

 caused by certain abnormal pressure or irrita- 

 tion to sensory nerves. After the pressure or 

 irritation is relieved the pain stops. In the 

 ordinary operation, pain would be caused by 

 the knife cutting through the skin. That is, 

 the instant the knife presses upon a sensory 

 nerve it causes pain, but as soon as the knife 

 has passed through the nerve and ceases to 

 make pressure the nerve is paralyzed and 

 causes no more pain unless its stump be irri- 



20 



