CHAP. IX.] 



THE CONTRACTILE TISSUES. 



355 



phoric acid was then added without causing any discharge. The acidified 

 muscle was heated to 50C., and thereupon liberated quickly a quantity of 



Thus the change in gaseous composition which muscle undergoes 

 on passing into rigor may be summarized as a large increase of that 

 carbonic anhydride which is denned as free, or capable of simple 

 withdrawal by an air-pump. 



The discharge of gases is a primary phenomenon of rigor and 

 not due to the decomposition of carbonates already existing in the 

 muscle, by the acid formed in the same process. For the addition of 

 phosphoric acid at a time when the discharge is free, tends rather to 

 diminish the total discharge than increase it, and never leads to an 

 evolution of gas proportionate to the yield of free carbon dioxide. In 

 other words, the. carbon dioxide is formed step by step with the pro- 

 cess of rigor ; but, although it is actually formed during rigor, it may 

 still first appear in some fixed and stable modification ; and this is a 

 possibility which we have as yet no means of testing 2 . 



Gaseous With very similar appliances to those just described 



analysis of the gaseous alterations of muscle during activity may 

 contracting b e determined ; but this research is beset with great 

 difficulties, if a complete analysis of the gases is 

 desired. In the first place it is indispensable to employ boiled salt- 

 solution and to use scrupulous care in excluding air-bubbles. In the 

 second, there is great danger of electrolytic action due to the strong 

 currents needed to stimulate muscles immersed in salt-solution. And 

 in the third, it is impossible to adopt wholly the method of tritu- 

 ration in order to facilitate the escape of gas in the vacuum ; all 

 that may be attempted for this purpose is to mince the muscle 

 coarsely, or to select muscles of small bulk like the sartorius. But 

 many of the difficulties of experiment may be avoided after it has once 

 appeared that, as in the case of rigor, carbon dioxide is the only 

 important constituent. No oxygen is ever detected ; and the nitrogen 

 evolved behaves like the nitrogen set free in the rigor of muscle. 

 Hence it is at once possible to dispense with the troublesome salt- 

 solution and the strong tetanizing currents ; and to examine muscles 



1 Hermann, Op. cit. p. 114. 



Hermann, Op. cit. p. 16. 



232 



