290 



Dr. A. Forbes. Reflex Rhythm 



[Apr. 11, 



be deeply submerged than if near the surface, so the nerve impulses might 

 be rendered more intense and more infrequent in overcoming the opposing 

 influence of inhibition. 



On account of the impossibility of recording nerve impulses with the 

 myograph I have planned to investigate the question by electrical methods. 

 But in the course of another series of experiments I have obtained records 

 whose bearing on the problem renders them of interest. 



II. Method. 



In the experiments in which these records were obtained the method was 

 that employed throughout the experiments already reported.* Briefly, it was 

 as follows : — The animal (cat) was decerebrated under ether (or chloroform- 

 ether) anaesthesia. All or nearly all muscles were paralysed by section of 

 their nerves, except the right vastocrureus (knee extensor). In some cases 

 the right peroneal nerve was stimulated to produce reflex inhibition and the 

 left popliteal nerve to produce reflex excitation ; in some cases the whole left 

 sciatic nerve was used for excitation, and either the whole right sciatic nerve 

 or the right popliteal or peroneal was used for inhibition. The femur was 

 fixed, and the apparatus so arranged that contraction of the vastocrureus 

 muscle was shown by a rise in the myograph line. 



The afferent nerves were stimulated by faradisation from two induction 

 coils. The primary current, common to both, was interrupted between 30 

 and 50 times a second by a circuit breaker run by a motor. In the later 

 experiments (at Liverpool) a commutator was introduced into the secondary 

 circuit used for inhibitory stimuli, so arranged that it delivered to the nerve 

 only break shocks and those alternately in ascending and descending direction. 

 Defects which resulted from wear of the commutator after many experiments 

 appeared to have an important effect on the reflex responses which will be 

 discussed later. 



The strength of the stimuli was estimated in accordance with Martin's 

 scale.f In the earlier experiments (at Harvard), coils calibrated by him were 

 employed. In the later experiments (at Liverpool), an empirical approxima- 

 tion to Martin's units was used. 



III. Observations. 



Two types of observation are dealt with here ; those in which two afferent 

 nerves were simultaneously stimulated, and those in which only one nerve 

 was stimulated. 



* " Keflex Inhibition of Skeletal Muscle," in course of publication in ' Quart. Joura. 

 Exp. Physiol.' 

 t ' Amer. Journ. Physiol.,' vol. 22, pp. 61 and 116. 



