THE CONQUEST OF DISEASE 



nates in the sensory nerves which transmit cer- 

 tain sensations to the brain, which are inter- 

 preted as pain. These sensations can only orig- 

 inate in these particular nerves. Pain is not 

 Pain a spe- a general sense which may come from every 

 cial sense. part of the body. It is a special sense, as much 



as smelling or hearing. The subcutaneous tis- 

 sues, the muscles and organs are almost with- 

 out sensation. An internal organ can be rup- 

 tured or a great muscle divided with little or 

 no pain excepting when a sensory nerve trunk 

 is injured. The brain itself is without sensa- 

 tion. A knife or needle may be inserted into 

 the human brain, it may be lacerated or large 

 pieces of brain removed, with no pain being 

 experienced. Our horror of pain is derived 

 chiefly from our knowledge of the skin and the 

 mucous membranes which are continuous with 

 it. This pain-appreciation is, moreover, de- 

 pendent upon the mental development of the 

 individual. Primitive peoples have an insensi- 

 tiveness to pain which is beyond our compre- 

 hension. Their self-mutilations are made 

 possible not by bravery but by this low degree 

 of pain-sense. The savage who chops off his 

 hand and presents it to the king has displayed 

 a stoicism which is comparable to that of the 



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