ORIGIN OF LACTIC ACID FROM SUGAR 459 



came to the conclusion from these results that both the carbo- 

 hydrates and the proteins are to be regarded as contributing 

 to the formation of lactic acid, the former, it is true, ap- 

 parently in much the greater proportion. This harmonizes 

 closely with the latest researches upon the nature of gly- 

 colysis, dealt with above (vide supra, p. 338). Just as sugar 

 by the isolated influence of alkali is broken down with ex- 

 treme readiness into lactic acid, we have every reason for 

 assuming that physiologically also glycolysis gives rise to 

 lactic acid, 18 and that the formation of lactic acid observed by 

 J. Miiller in the surviving cat's heart, for example, is due to 

 direct cleavage of grape sugar. Apparently a portion of the 

 lactic acid coming from sugar cleavage in the economy is 

 changed into " lactacidogen, " which later under certain con- 

 ditions, as in postmortem acid change, again gives rise to 

 lactic acid. " Apparently," says Embden, 19 "the principal 

 route of carbohydrate catabolism in the economy is by way of 

 lactic acid ; and in lactic acid the greater part of the chem- 

 ical energy which was in the glucose is still present. ... .. . 



The very fact that a predecessor of lactic acid, which is very 

 easily convertible into lactic acid, is at the disposal of the 

 musculature, permits one to surmise that lactic acid is the 

 most substantial source of muscular power. ... It 



should be recalled that the older and particularly, too, re- 

 cent authors regard it as very probable that a definitely local 

 lactic acid production within the muscle is concerned with 

 the relaxation of contracted muscle. For the purpose of 

 rapid production of lactic acid this predecessor of lactic acid, 

 which is apparently not of acid nature or at least less acid 

 than the lactic acid, may, perhaps, have an important part. ' ' 

 The author's ideas based upon his personal studies as to the 

 role of lactic acid in bringing about and relaxing rigor mortis 

 have been discussed in a previous lecture (v. Vol. I of this 

 series, p. 135-147, Chemistry of the Tissues). 



18 Cf. J. H. Ryffel, Jour, of Phyaiol., 40, Proc. Physiol. Soc., LI, 1910. 

 "G. Embden, F. Kalberlah and H. Engel, Biochem. Zeitschr., 45, 45, 1912. 



