80 Chapter VI 



the chemical activity, whether expressed as heat or as the call for 

 oxygen, is not merely something which accompanies the contraction 

 of the muscle, but the contraction sets going a chain of chemical 

 events which are necessary for the restitution of the muscle into its 

 former state ; that the increased functional activity is responsible 

 for the increased oxidation is certain. 



In the light of what has since been published one is inclined to 

 wish that the actual work done by Verzar on muscles had been of a 

 more definite character. It consisted of lifting a weight and keeping 

 it (or failing to keep it) at the height to which it had been lifted. 

 Clearly this is a very complex process. The first portion of it is readily 

 to be expressed in grm.-cms., the second is somewhat illusory and at 

 once brings us to the brink of controversy. We must avoid the 

 use of vague terms such as statical work. In some further, as yet 

 unpublished, experiments Hill has shown that the heat produced by 

 a sartorius muscle of the frog in maintaining for 1 second a tension 

 of 1 gram weight in 1 centimetre of muscle length is, including 

 recovery processes, about 25 x 10~ 6 gram-calories. This exceedingly 

 large number corresponds to the oxidation of 6 x 10~ 9 grams of 

 carbohydrate, which would correspond to an amount of O 2 used, 

 4*4 x 10~ 6 c.c. In Verzar's experiment there was 0*5 c.c. of O 2 used, 

 as a result of 25 sec. stimulus, or an average amount of 0'02 c.c. 

 per sec. In a muscle 5 cm. long Hill's number should give about 

 22 x 10~ 6 c.c., so that if his result is comparable with Verzar's, the 

 gastrocnemius used by Verzar would have exerted a tension of 

 1000 grams weight in an isometric contraction. It is a pity that 

 Verzar's experiment was not conducted isometrically and the ten- 

 sion exerted expressed in absolute units. In all future work on the 

 subject, isometric contractions, as Hill has repeatedly urged, should 

 be used. In any case it is very striking that the tension that could 

 be exerted, according to Hill's figures, is exactly of the right order 

 of magnitude. The gastrocnemius preparation of the cat, as used by 

 Verzar, could certainly lift about 1000 grams weight. It would be 

 of the greatest interest to ascertain exactly the amount of O 2 used 

 by a muscle in maintaining a tension, per second, per gram weight 

 of tension maintained, per centimetre of muscle length. As Hill has 

 urged, the tension exerted and not the work done is the fundamental 

 quantity in the muscle: and therefore the O 2 used in maintaining 

 unit tension for unit time on a muscle of unit length is the funda- 

 mental unit of oxidation. 



The Heart The pioneer work on this subject was carried out by 



