90 



CONSCIOUS NERVOUS OPERATIONS 



by which a sense of pain is conveyed when they are more 



strongly stimulated. 



119. Path of a Touch Impression. Let a touch corpuscle 



be stimulated by pressure, and what follows ? (Fig. 52.) 



The cells of the end 

 organ communicate 

 the impulse to the 

 afferent nerve fibers 

 passing from the 

 touch corpuscles to 

 the nerve distributed 

 to that part of the 

 skin. The sensory 

 nerve fibers may run 

 through more than 

 one nerve plexus and 

 through ganglionic 

 nerve centers. There 

 may be several breaks 

 in the path, where 

 the original impulse 

 is handed over from 

 one fiber to another, 

 or passes from cell 

 to cell, or from fiber 



Fig. 52. Diagram of the path of a touch 

 impression. 



The dotted lines show the path when the im- 

 pulse ascends to the brain, exciting conscious- to Cell ; but the 

 ness, and through the motor center (MC), 

 producing voluntary motion. 



pulse finally reaches 

 the spinal cord (ex- 

 cept when a cranial nerve conveys the impulse), through 

 a posterior nerve root, and the cells of the gray matter of 

 the cord are stimulated. 



But there is yet no sensation, even though by the reflex 

 action of the cord a motor impulse may be sent out by an 



