226 IRRITABILITY 



the eighth or the seventh root is stimulated with stronger faradic 

 shocks during the time when tetanus is produced reflexly by 

 faradic stimulation of the ninth, an inhibition is practically always 

 obtained. Indeed, faradic currents that are so weak as to be far 

 below the threshold of perceptible response bring about when 

 applied to the seventh or eighth root a decided inhibition of the 

 tetanus, brought about by simultaneous stimulation of the ninth 

 root. The inhibitory effect of weak sub-threshold excitations 

 are here particularly apparent. This inhibition resulting from 

 excitation far below that of the threshold of perceptible response 



Fig. 59. 



is a common occurrence in the functional activities of the central 

 nervous system. In various parts of the nervous system, the 

 excitation in its conduction is weakened when passing through 

 intervening ganglion stations so that it has undergone a strong 

 decrement before reaching the responding structure, where an 

 inhibitory effect may be manifested. In this connection it is of 

 interest that the reciprocal "antagonistic reflexes" discovered by 

 Sherrington,^ who recognized their importance in the fflnctional 

 processes of the nervous system, can be explained, as Frohlich 

 showed, upon this principle of inhibition resulting from weakened 

 excitation. On the basis of numerous investigations in the 



1 Sherrington: "Experimental note on two movements of the eye.*' Journ. of Physi- 

 ology XVII, 1895. The same: "On the reciprocal Innervation of antagonistic mus- 

 cles." Proceed, of the Royal Soc, 1897. 



