FK;. 174. INHIBITION OF TONIC CONTRACTION. 



1. A, Reflex contraction of vasto-crureus muscle in decapitated cat. At the rise of the signal 1, the 

 ventral end of an inhibitory nerve (ipselateral peroneal) was stimulated. Since the muscle was free 

 from tonus, no apparent result was obtained. At the rise of the signal C, an excitatory nerve (con- 

 trilateral peroneal) was stimulated a certain degree of contraction. When the inhibitory 

 stimulus was removed, there was a much greater contraction, showing that the previous condition 

 was one of balance. Time in seconds above. 



1. B, A similar experiment, with relatively greater strength of inhibitory stimulus. The grade of con- 

 traction is less than in 1, A. 



Note the continued steady position of the muscle in the different degrees of relaxation. 



2. Vasto-crureus in decerebrate rigidity. Reflex inhibition produced by stimulation of the ipselateral 

 peroneal nerve, with slowly repeated break induction shocks shown by signal lines SA to SB. 

 Time in fifths of seconds by signal TA TB. 



In experiment A, the strength of the stimulus was greater (100 Kronecker units) than in B (20 

 Kronecker units). In both, the relaxation proceeds to the full resting length of the muscle ; but, 

 in A, it is rapid and attained after nine shocks, while in B it is reached slowly in eighty -si v 

 shocks of the weaker stimulus. The signal line at the foot of the figure marks the'duration of the 

 stimulation in />'. 



Note that no permanent intermediate state, due to balance of degrees of excitation and inhibition, is 

 obtained in this state of decerebrate tonus. 



(Sherringtou, 1909, 2, pp. 256-257.) 



