384 PHYSIOLOGY 



inhibition of the flexor tone is thus not determined by the increased 

 tension of the flexors, but is a direct result of the primary cutaneous 

 stimulus. 



B 



Fifc. 170, A and B. (SHERRINGTON.) 



The flexion reflex observed as reflex contraction (excitation) of the flexor 

 muscles of the knee (A), and as reflex relaxation (inhibition) of the extensor 

 muscle (B). The stimulus was a series of weak break induction shocks 

 applied to a twig of the internal saphenous nerve below the knee. Observa- 

 tion B was made four minutes after A. Note the summation of stimuli, in 

 each case six stimuli being required before the reaction was evoked. 



From a broad standpoint the function of the nervous system is 

 the co-ordination of all the activities of the body, so that these may 

 be combined to one common end, viz. the preservation of the organism. 

 For this purpose there must be no clashing between opposing activities 

 of different parts. If one part is engaged in any action this action 



