1912.] Induced by Concurrent Excitation and Inhibition. 293 



however, marked irregular oscillations appeared and continued as long as 

 the combined stimulation was maintained. 



In a third animal in which decerebrate rigidity was not marked, the 

 inhibitory stimulus was made strong enough to reduce the contraction of 

 the muscle to about half the amount produced by the excitatory stimulus 

 alone. The oscillations, which were even more marked than in the case 

 described above, are shown in fig. 2. The excitatory arc was stimulated 

 with 9 units, the inhibitory arc with 5 - 5 units. Here it will be seen that 

 the muscle was in a state of tremor when the excitatory stimulus was first- 

 applied, but the resulting contraction was comparatively free from tremor ; 

 then, when the inhibitory stimulus was added, the resulting relaxation was 

 immediately followed by irregular oscillations at a rate of four or five a second. 

 With continuance of the combined stimulation these became more marked and 

 more regular, and slowed to a rate of about one a second. 



In a more recent experiment at Liverpool, similar but less marked 

 oscillations were obtained by simultaneous opposed stimuli (fig. 3). Here 

 the inhibitory stimulus was applied to the whole sciatic nerve. The 

 electrodes had been in contact with the nerve for a long time, and local 

 impairment had occurred. The strong stimuli indicated in the figure do not, 

 therefore, represent correspondingly strong central stimuli. The oscillations 

 occur at a rate of about eight or ten a second. 



Fig. 3. — Time-marker records in seconds. (Liverpool.) 



