CHAP. IX.] 



THE CONTRACTILE TISSUES. 



373 



dioxide exhaled is due, in the first place, to the increased production 

 of it within the muscle during, tetanus 1 ; and in the second to the 

 increased facility for its escape offered in the agitation of the muscle. 



The following experimental figures will serve to illustrate the extent of 

 the gaseous exchanges of muscle 2 . 



Experiment. Comparison of gaseous exchanges of living muscle, and 

 muscle made rigid by exposure to a temperature of 45 C. 



Duration of experiment 19h. 15 m. Temp. 14 17C. Gases estimated 

 at and 1 mtr. 



1. Living muscle = 7-352 grms. = 6*948 c.cm. 



2. Rigid muscle = 7 '6 31 grms. = 7 -2 13 c.cm. 



Experiment. Comparison of the gaseous exchanges of muscle in repose 

 and in tetanus. 



Tetanus induced at intervals during the experiment. 



Duration of the experiment 3 h. 10m. Temp. 15 16 C. Gases esti- 

 mated at and 1 mtr. 



1. Resting muscle = 9*468 grms. = 8*949 c.cm. 



2. Tetanized muscle = 9*480 grms. = 8 -960 c.cm. 



B. Changes in the chemical composition of the medium surrounding 



muscle. 



ft. When muscle is still in the body. 



In the previous section, we have discussed the so-called 

 'respiration' of muscles removed from the body, or the gaseous 

 exchanges between excised muscles and their surrounding medium; 



1 See the preceding section. 



2 Hermann, Op. cit. pp. 123, 125 : Expts. 23 and 27. 



