Reflex Nervous Discharge. 



271 



stimuli may be followed by as many as 3-5 muscular action-current waves. 

 The well-known slow subsidence of contraction frequently met as the after 

 effect (T. Graham-Brown's* terminal phenomenon) seems an instance of the 

 same kind, though more pronounced. 



For our observations the muscle used was tibialis anticus, the preparation 

 a spinal cat previously decerebrated under chloroform, the afferent nerve the 

 popliteal, and the stimulus a single break-shock obtained by opening the 

 primary circuit by a pendulum key set similarly throughout the whole series 

 of experiments. The muscular contraction was recorded by an isometric 

 myograph whose own vibration period was much shorter than that of the 

 simple muscular twitch and damped to give it some " dead-beat " character. 

 After the samples of reflex contraction had been obtained by stimulation of 

 the popliteal nerve, the peroneal nerve, innervating tibialis anticus, was 

 severed and the stimulus, arranged to be maximal, was applied to the 

 distal stump of this motor nerve itself. The break-shock cathode was 

 placed proximal on the afferent nerve for the reflex, distal on the motor 

 nerve for the " direct " twitch. The preparation and its attachment to the 

 myograph remained unaltered. The interval between the two observations 

 was sometimes only four minutes, the electrodes and interelectrodal distance 

 remained the same for both. Contraction curves showing duration and 

 tension-height concurrently were thus obtained for the same muscle both in 

 its reflex and direct response in the same individual preparation using a single 

 break -shock stimulus delivered by the same key. 



The condition of the preparations was usually very good, judging from the 

 lowness of the threshold stimulus, both reflex and peripheral. It is to be 

 regretted that the stimulus value was not obtained by the Martinf method, 

 but the apparatus for that has not been at hand for us. The values taken 

 were readings of the Berne inductorium scale, the primary fed by a 2-volt 

 cell. The threshold readings were often very low indeed, far below 30 

 Berne units ( = 27 cm. on the ordinary scale), e.g., 30 units — 70° angular 

 turn of the secondary spiral, sometimes 30°-80° Often the difference 

 between the threshold for the reflex and for the motor-nerve observation 

 was only a few degrees of the angular scale. 



Besults. — Our graphic records of the reflex contraction to the single 

 break-shock have not rarely been very similar to those of the twitch- 

 contraction to the shock applied to motor nerve itself. This has been so 

 most frequently when the break-shock stimulus for the reflex is near 

 threshold value ; it is the case also sometimes when the break-shock 



* T. Graham-Brown, 'Quart. Journ. Exp. Physiol.,' vol. 7, p. 199 (1914). 

 t E. G. Martin, ' Measurement of Induction Shocks,' New York, 1912. 



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