EXCITATION AND INHIBITION 



413 



producing its normal fall of blood pressure ; this fall is interrupted, temporarily, 

 during the rise of the lowest signal line, by a return to normal, resulting from 

 simultaneous stimulation of an ordinary afferent nerve, the anterior crural, which, 

 on its own account, would have produced a rise of arterial pressure above normal 

 by excitation of the constrictor centre. The effect of this nerve lasts longer 

 than the period of stimulation, but the continued stimulation of the inhibiting 



^"isf 



tK<^ C 



S g 



er 

 er ex 



gl 



ag 



rl> 



il 



g^s-g 



C -, 8 

 OT30 

 'B 6 j- o> 



1 1.1 1 



<N 



ti 

 S 



" 

 o> 

 oo 



42 



a s i 



Q. 5 | 



bf) _Ui .S 



X O3 H 



"88 



r: 



S fiS S 



S o s 



nerve makes itself felt again and the blood pressure rises finally to normal only 

 when the stimulation of the depressor ceases. 



In Fig. 122 two tracings are given from Sherrington's paper (1908) which 

 show the same fact in the case of reflexes to skeletal muscle. The vasto-crureus 

 muscle of a decerebrate cat traces its contraction by a rise in the curve. The 

 upper signal indicates by a fall the stimulation of an inhibitory nerve, the central 

 end of the peroneal of the same side, and the lower signal that of an exciting 

 nerve, the central end of the popliteal of the opposite leg. In A, the inhibiting 



