Reflexes, etc., of Mammalian Nerve-muscle. 257 



to excitation of more than very brief duration is rhythmic (tetanic). If, for the 

 convenience of avoiding periphrasis in referring to it, we speak of the central 

 process underlying and at back of the repetitive centrifugal discharge as the 

 " charge " in contradistinction to the " discharge " it evokes, one feature that 

 we may infer about the " charge " is its relatively long duration, i.e., relatively 

 to the whole cycle of a nervous impulse, and another is that, in response to 



■DODl.aOcm. 







m 



popf.25cin.. 



m.iscm. 



20cm. 



jrniin 









m.20cm, 



A 





B 



Fig. 8. — Upper record : reflex contraction of tibialis anticus (spinal cat) given by single 

 break-shock at 30 cm. coil distance to central stump of popliteal nerve, followed on 

 the same plate by record of maximal twitch given by single break-shock at 20 cm. 

 coil distance, cut motor nerve ; time ordinates at Jg sec. intervals ; tension abscissae 

 31 grm. per millimetre. Lower record, A, similar to above from another experiment : 

 the reflex by break-shock at 35 cm. coil distance, and the motor response distinctly 

 " supramaximal " by break-shock at 15 cm. ; the true maximal twitch, as determined 

 by subsequent trial, is given at B, the instance shown being with break-shock at 

 20 cm. coil distance. Stimulus-signal below. 



stronger break-shock stimuli of the afferent nerve, other conditions remaining 

 the same, it attains a given degree of intensity, or amounts to a given 

 quantity, more rapidly and dies out less soon than when such stimuli are 

 weaker. In searching for a refractory phase for it in the flexion-reflex, Miss 

 Sowton and myself (7) could find no positive evidence of such ; that is to say, 

 the period of refractoriness that was indicated for the I'eflex in our experi- 

 ments was so brief that it could be accounted for apart from the central 



