The call for oxygen by muscle 77 



Verzar's results have reformed our view as to the terms in which 

 we should express the increased oxidation which results from in- 

 creased activity. In treating of Chauveau and Kaufmann's work 

 we followed their method of stating their result when we said that 

 the " coefficient of oxidation " was increased say thirty -fold. This is 

 clearly an inadequate statement of the case. At a certain point in 

 the train of events the oxidation was increased to that extent. Really 

 we should ask, How much extra oxygen was used by the muscle as 

 the result of such and such a piece of work ? In order to answer 

 this question we must, it is true, consider the events taking place 

 during the work, but just as necessary is it to consider those taking- 

 place after it. 



The third of the three experiments quoted above gives the most 

 satisfactory data which we have at the present time for relating the 

 functional activity of the muscle and the oxidation taking place 

 within it. The duration of this experiment was long enough to allow 

 the oxygen consumption to return almost to its original level. We 

 can therefore, by calculating the whole increase in the oxygen used 

 during the period of the experiment, obtain a minimal value for that 

 required a value which is probably not very far from the true one. 

 Of the experiment in question one can say (1) that as the result of 

 the stimulus given, which lasted about 25 seconds, the muscle showed 

 increased oxygen intake for 220 seconds at least, and (2) that in this 

 time it used up 753 c.c. of oxygen as against '260 which it would have 

 used up at its normal rate ; therefore the stimulus which was given 

 was responsible for at least '5 c.c. of oxygen used by the muscle. 



The fact that the increased oxygen consumption of the muscle 

 survived the increased functional activity must be viewed in conjunc- 

 tion with the recent work of Hill' 4 ', who investigated the relation in 

 time of the functional activity of amphibian striated muscle and the 

 heat-evolution of the same. 



Hill's method was as follows : he compared the curve of de- 

 flection of a galvanometer registering thermo-electrically the rise of 

 temperature of a live muscle when stimulated, with the curve of 

 deflection given by the rise of temperature due to electrical warming 

 of the same muscle after death. He found that the curve of de- 

 flection (coming back to the base line in 4 or 5 minutes by reason 

 of heat-loss) was the same for a muscle in nitrogen as for a muscle 

 warmed after death by a very short tetanising current : there is 

 therefore in nitrogen no heat-production except in the few moments 

 immediately following an excitation. In O 2 however the curve of 



