Muscle during Maintained Contraction. 



409 



sciatic nerve, as shown in fig. 3, the end result corresponds to a decrease in 

 acidity. The initial result is still doubtful, as the figure reproduced shows a 

 movement of the mercury in the opposite direction before the inhibition 

 occurs. This result may be due to either a slight contraction before relaxa- 

 tion,* or setting free of acid from the muscle preliminary to its removal by 

 some other mechanism. 



Fig. 3. — Record of l'eiiex inhibition. Indications as in figs. 1 and 2, but relaxation of 

 muscle is shown by a line which starts above time marker and falls across it, instead 

 of the record of contraction shown below. Relaxation is accompanied by decrease 

 in acidity. 



The results indicate that acidity and tension in muscle are concurrent. 

 Thus it may be better to investigate, not how the contraction is maintained, 

 but why the acid remains and is not removed as in a simple twitch. The 

 results further suggest that as acidity is common to both tetanus and tone 

 probably the mechanism for the production of both is the same, i.e., that there 

 is one mechanism in muscle and not two. 



I wish to thank Mr. F. C. Smith for assistance in some of the experiments 

 on decerebrate eats. Some of the apparatus for the research was obtained 



* Sir Charles Sherrington informs me that weak reflex inhibition is frequently pre- 

 ceded by a slight contraction. This fact is in favour of the view that the slight 

 increase in acidity, shown before relaxation occurs, is due to a preliminary increase in 

 tension. 



