The Respiratory Process in Muscle. 



447 



to give a simultaneous fresh production of lactic acid and of carbon dioxide in 

 the absence of an immediate oxygen supply. The introduction of oxygen 

 and the preparation for combustion had taken place beforehand. 



(2) The instability of the inogen molecule increased with rise of tem- 

 perature, and so also the rate of production of lactic acid and carbon 

 dioxide, but it was believed that, if the muscle were scalded suddenly with » 

 boiling water, the molecule could be " fixed " without a yield either of lactic 

 acid or of carbon dioxide. 



The evidence under both these heads was first examined by one of us so 

 far as the carbon dioxide production was concerned (1). 



It will be enough now to recall that in this work improved titration 

 methods were used for the estimation of cat'bon dioxide, in place of 

 Hermann's eudiometric method, and that the new knowledge of bacterial 

 action allowed the results of early putrefaction to be recognised and left out 

 of account. 



By successive estimations, the course of carbon dioxide discharge from 

 isolated frog's muscle was followed. At rest the muscle gave a high initial 

 rate of discharge, which soon descended to a lower rate, maintained at steady 

 level for many hours. 



When the muscle was stimulated to contract, an outburst of carbon 

 dioxide such as Hermann had found, and as all the text-books of the 

 day described, was expected and looked for, but none was found ; no 

 increase of carbon dioxide accompanied contraction unless the contraction 

 was forced by repeated strong stimulations to give marked fatigue. 



At rest again, the muscle in nitrogen gave a lower steady output of carbon 

 dioxide than in air ; in oxygen it yielded carbon dioxide two or three times as 

 fast (fig. 1). 



. — i in air 

 in oxygen 



beginning of oxygen 

 supply ,to one 



Hours 12 3 4 

 niter excision. 



8 9 10 11 12 



22 23 24 25 



1. — Survival discharge from " crossed " pairs of legs, one in air, the other in oxygen. 

 From the ' Journal of Physiology,' vol. 28, p. 354 (1902). 



