1912.] 



Rhythmic Activity of the Nervous System. 



281 



a b c d 



Fig. 1. 



Experiment 30, 31.3.11. — Ordinary decerebrate preparation, a series of four reactions. 



In the first of these (a) a simple contralateral stimulus is applied between the marks A, B, of 

 the signal line (ordinates a, a' ; b, b'). This evokes a simple reaction of maintained extensor 

 contraction — the crossed extension-reflex. 



In the second of these (b) a simple ipsilateral stimulus (signal X, Y — ordinates x, jo' ; y, y 1 ) 

 evokes a simple reaction of maintained flexor contraction — the ipsilateral flexion-reflex. 



In the third of these (c) the contralateral stimulus is first applied (A — B) and then evokes 

 maintained extensor contraction. During this stimulus an ipsilateral one is added (X — Y). This 

 gives a smaller flexor contraction than in " b," and at the same time there is a rhythmic 

 movement in the extensor tracing. 



In the fourth record (d) both stimuli are applied at once, and the extensor movement — the 

 latency of which is increased — is rhythmic from the first. 



The strengths of the ipsilateral and of the contralateral stimuli remain the same throughout 

 this series. 



In all the figures the upper tracing is that of the flexor— tibialis anticus, and the lower that of 

 the extensor — gastrocnemius. The upper signal line is that of contralateral stimuli, the lower that 

 of ipsilateral. The lowest line marks seconds and millimetre scales are reduced in proportion 

 with the tracings. Corresponding ordinates on the tracings mark the beginnings and 

 terminations of the stimuli, and the rise of the levers denotes contraction of a muscle — the fall 

 relaxation. 



VOL. LXXXV. — B. 



U 



