336 



Dr. K. Sassa. Observations on Reflex 



peripheral tetanus produced increases with the strength of stimulation, until 

 the maximum is obtained for any given frequency-rate, and beyond this 

 point there is no decline, but an unvarying response is given with pro- 

 gressively increasing stimuli. 



The experimental results here described concerniug the inHuence of intensity 

 and frequency of stimulation upon the reflex response are in accord with the 

 observations of Wedeusky (19), Hoffmann (9) and others, on peripheral 

 tetanus, usually spoken of as " Wedensky's phenomena." When the muscle is 

 tetanised from its motor nerve with strong induction shocks of considerable 

 frequency it relaxes more or less quickly. If the stimuli are then weakened 

 to a certain extent the muscle again falls into a powerful tetanus (Optimum der 

 Eeizstarke). If, however, they are again strengthened it enters into its 

 former relaxed condition (Pessimum der Eeizstarke). A similar result is 

 obtained by altering the frequency at high intensity of stimulation. For the 

 fresh muscle of the frog, the optimal frequency of stimulation, at which the 

 highest contraction is obtainable in the shortest time, is about 100 stimuli 

 per second (60-150). When lower frequency (about twenty per second) or 

 higher frequency of stimulation (over 260 per second) is used the muscle 

 never attains its maximal shortening in any phase of tetanus. If the prepara- 

 tion is in an unfavourable condition as a result of fatigue or poisoning by 

 ether or curare the optimal frequency of stimulation is lower and the optimal 

 intensity is obtained at lower frequency. On comparing the results in 

 peripheral and reflex tetanus under normal conditions, the most noteworthy 

 difference is that in the latter the optimal frequency of stimulation is lower 

 than in the former ; the latter, therefore, only corresponds to the former , 

 when the preparation is under unfavourable condition. Another striking 

 difference, though not a constant one, is seen to exist between direct and reflex 

 tetanus produced by pessimal intensity of stimulation. The muscle, in the 

 latter case, often enters into a more exaggerated contraction or goes into 

 contraction (if this has not been present during its course) when the stimula- 

 tion is discontinued. The after-discharge which appears in any reflex 

 contraction does not usually surpass the height of tetanus obtainable during 

 the application of stimulation, except when the reflex is produced by pessimal 

 intensity of stimulus. 



These observations on optimal intensity have a superficial resemblance to 

 those of Sherrington and Sowton (17) on the tonic contraction of the knee- 

 extensor which was augmented by weak stimulation and inhibited by 

 stimuli of stronger intensity. A similar change of response to stimuli of 

 altered intensity is exhibited by the opening muscle of the claw of the cray- 

 fish (3, 7, 13, 15). 



