510 



Mr. K. Lucas. 



[June 6, 



out a characteristic effect of the drugs Yohimbine and protoveratrine, 

 namely the association of a great prolongation of the declining phase of 

 the electric response with a great lengthening of that part of the refractory- 

 state which is marked, not by complete inexcitabilitv, but by the need of 

 stimuli of abnormal strength. On these facts he founds the hypothesis 

 that the period of complete inexcitabilitv corresponds to the rising phase 

 of the electric response, that of only relative inexcitabilitv to the declining 

 phase. The facts on which this hypothesis rests are of obvious significance, 

 but the interpretation put upon them cannot be justified without a thorough 

 simultaneous measurement of the phenomena. It will be enough here to 

 recall one pair of measurements which can be gathered from the general 

 literature of the subject, in order to indicate that Tait's hypothesis will need 

 more stringent proof before it can be accepted. Bazett* found that in the 

 sartorius muscle of the frog a fall of temperature of 10° C. prolongs the 

 refractory period by more than 200 per cent. ; over the same fall of tempera- 

 ture and in the same tissue I foundf that the ascending phase of the electric 

 response is prolonged by not more than 70 per cent. If these results are 

 valid the two phenomena, though of like duration at one temperature, cannot 

 remain so when the temperature is changed. 



We have much still to learn about the relationships of the refractory 

 state. But its recognition as a part of the process of propagation cannot 

 fail to be a significant fact for any hypothesis of the propagated disturbance. 

 It is already suggestive that the effect of temperature change on the process 

 of recovery should be so widely different from that produced on the rate of 

 propagation. Maxwell^: first showed that the effect of a fall of 10° C. is an 

 increase of the time of conduction in slug's nerve of the order of 80 per cent., 

 and values of the same order have since been found for amphibian nerve and 

 muscle. § To set against this we have Bazett's observation of more than 

 200 per cent, increase in the refractory period. This value needs to be 

 checked for other tissues, and particularly for nerve, but we can scarcely 

 doubt that it will prove a significant fact when we reach the point of 

 formulating a definite quantitative hypothesis of the propagated disturbance. 



D. The Contraction Process. 

 Up to this point the processes into whose position we have enquired have 

 all been such as occur in nerve as well as in muscle. In turning now to 



* Bazett, loc. cit. 



t Keith Lucas, ' Journ. Physiol.,' 1909, vol. 39, p. 207. 



% Maxwell, 'Journ. Biol. Chem.,' 1907, vol. 3, p. 359. 



§ Keith Lucas, 'Journ. Physiol., ; 1908, vol. 37, p. 112 ; Woolley, ibid., p. 122. 



