352 Dr. K. Sassa. Effects of Constant Galvanic Currents upon 



absent, and only inhibitory reflex effects can be obtained. No rebound 

 phenomenon occurs even after strong stimulation. Plastic reaction is, however, 

 fairly easily obtainable. At a certain stage of anaesthesia, a preparation 

 showing typical reflex responses of excitation and inhibition before adminis- 

 tration of the drug is converted to one in which the excitatory reflex effect 

 is entirely excluded. The ansesthetie (chloroform and ether) can convert an 

 excitatory into an inhibitory reflex effect, as was first pointed out by 

 Bayliss (1) in the case of the vasomotor pressor reflex, and by Sherrington 

 and Sowton (13) in the vasto-crureus reflex preparation. In other prepara- 

 tions, on the contrary, excitatory effects are obtained with comparatively 

 strong currents in either direction. Only the strongest stimulation of the 

 afferent nerve produces relaxation of the tonic contraction of the muscle, and 

 the inhibition is always followed by a marked rebound contraction. 



(ii) Another condition which influences the excitatory and inhibitory 

 effects is the initial length of the muscle. The muscle in the lengthened 

 condition reacts by excitation more easily to any stimulation, and in the 

 shortened condition by relaxation. If the functional condition of the tonic 

 centre favours the extensor tone, the reflex effect as obtained by weak 

 stimulation of tlie afferent nerve is often excitation, whether the muscle be 

 lengthened or shortened. The contraction in the former condition is always 

 more ample than that in the latter. Conversely, if the condition of the tonic 

 centre is unfavourable to the tone of the extensor muscle, the reflex effect is 

 usually relaxation, irrespective of the length of the muscle, especially with 

 strong stimuli. The inhibitory relaxation is always greater in this case, the 

 more shortened the muscle. Between these two extremes it is often observed 

 that reflex contraction is induced by a given stimulus when the muscle is 

 lengthened, while the inhibition takes place with the same stimulus when it 

 is shortened (fig. 4). 



It has been noticed that the posture of the limb influences and can even 

 reverse the direction of reflexes obtainable from the limb (6, 8, 9). But such 

 observations have rested on experiments in which there has been no actual 

 isolation of the muscle which responds to the reflex stimulus employed. In 

 the present instance the observations I have obtained have been made on the 

 actually isolated muscle. 



(iii) The position of most of the other joints in the body has some influence 

 upon the mode of reflex reaction (Beritoff(2), Magnus (6)). Above all, the 

 position of the neck in regard to the trunk and that of the head in space 

 must be kept constant throughout the experiment when the relation between 

 excitatory and inhibitory reflex effects is under investigation. Eeflex 

 reversal is often obtained by twisting the neck from one side to the other (tig. 5). 



