Reflex Nervous Discharge. 



275 



Various strengths of stimulus were used, and various heights of tetanic 

 contraction resulted, and all showed fine tremor of 65-per-second frequency. 

 The same " resonance " method, when applied to tetani similarly provoked, 

 but through the motor nerve direct, instead of through the afferent nerve 

 and reflex centre, similarly gave tremor of 65-per-second rate, somewhat 

 more marked in degree than with the reflex tetani A resonance method is 

 obviously open to some fallacies. Any movement of the recorder is liable to 

 be accompanied by undulations of the periodicity proper to the recorder. 

 But the continuance of the vibration throughout the long flat top of each 

 tetanus record argues that underlying that there was a muscle vibration 

 with which the lever's own period truly synchronised. 

 (3) The applicability both of the first mentioned " synchronous rhythm " 



Fig, 3. — Reflex response of tibialis anticus (spinal cat) to faradisation of afferent nerve 



(popliteal) at 60 per sec. 



method and the " resonance " method, for the purpose in view, depends 

 obviously on two conditions. The individual centrifugal impulses composing 

 each volley must be very approximately simultaneous ; if they are not so, the 

 end of one volley will commingle with the beginning of the next, and, the 

 muscle contraction examined being that of its fibre-complex as a whole, the 

 contraction waves will merge and may become inseparable in the record. 

 Also, even though the successive centrifugal impulse-volleys remain discrete, 

 the sluggishness of the contraction wave itself sets a limit to the separate- 

 ness of successive waves when they follow at rates higher than a certain 

 number per second, which number may conceivably be much lower than that 

 at which the reflex centre can still discharge discrete impulse volleys. This 

 limitation, due to the relatively prolonged apex-maximum of each contraction 

 wave, can be determined by recording the tetanic contraction of the muscle 



