RECIPROCAL INNERVATION , 



277 



In the skeletal system the mechanism of inhibition and 

 of reciprocal innervation is situated centrally. An active 

 state in an afferent nerve is converted centrally into a 



Fig. 44. — Diagram indicating connections and actions of two affei'ent 

 spinal root cells a and «' in rcgai'd to their reflex influence on the 

 extensor and flexor muscles of the two knees. The i-ign + indi- 

 cates an excitatory and the sign — an inhibitory effect (Sherrington). 



double effect — a positive effect upon one group of neurones 

 and a negative effect upon another. Central inhibition is, 

 however, not confined to the skeletal system. The 

 depressor nerve arising in the heart and aorta inhibits a 



