CHAP, in.] OP MOVEMENTS IN THE ANIMAL KINGDOM. 355 



We know that this change of coloration is the indication of 

 important chemical mutations. Thus, the venous muscular blood 

 which, in the state of repose, contains only 6,75 per cent of car- 

 bonic acid more than the arterial blood, contains 10*79 per cent, 

 after the contraction. 



An experiment of Matteucci has demonstrated in another 

 manner that muscular contraction corresponds to an oxydation of 

 the fibre. In two glass vessels of the same size the same number 

 of frogs, skinned and prepared, was suspended. In one of these 

 vessels the frogs were suspended to metallic hooks, .through which 

 was made to pass an electric current, which determined contrac- 

 tions. At the end of five minutes the frogs were taken out of 

 the vessels, into each of which the same quantity of limewater 

 was poured. Thus resulted in the two vessels precipitates of 

 carbonate of lime. But the precipitate was very slight in the 

 vessel where the frogs had remained immobile ; on the contrary, 

 it was very abundant in the other. 



All oxydation, in some degree energetic, has, for effect, a 

 certain development of heat. Thus it can be demonstrated, that 

 during contraction the muscular venous blood is hotter than the 

 arterial blood. 



But the production of carbonic acid in the living tissues 

 results from and is accompanied by many other chemical muta- 

 tions ; also we see that the contractions alter the composition of 

 the muscular juice bathing the fibre. In the state of repose, 

 when the muscle is not fatigued, this muscular juice is abundant 

 and its reaction is neutral or alkaline. The existence of this 

 liquid and alkaline medium is necessary to contractility. In 

 effect, a muscle into which a liquid even slightly acid is injected, 

 loses the faculty of contraction. 



The alkaline muscular juice of the muscle in repose contains 

 oxygen, creatine, creatinine and other analogous substances, 

 which are products of oxydation of the albuminoids. 1 We find 

 therein also sugar, lactic acid and potash. It is this last substance 

 1 Cl. Bernard, loc. tit., pp. 226, 227, 170. 



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