456 LACTIC ACID 



and formic acid by distillation with fifty per cent, sulphuric 

 acid: 



CH 8 



CH, + H 



CHJOH -I I 



COH COOH. 

 COOH 



The aldehyde is then estimated colorimetrically by the hand- 

 some red color which it strikes with a rosaniline solution 

 decolorized with sulphurous acid. 8 



Postmortem Formation of Lactic Acid. We may at this 

 point take up again the striking features of the present 

 status of the lactic acid problem. 



It should be definitely understood that as sources of lactic 

 acid we must keep in mind carbohydrates, proteins, and, too, 

 a substance of unknown nature, which may be characterized, 

 following the suggestion of Embden, as lactacidogen. The 

 chemical relation with carbohydrates may be seen in the 

 very readily occurring decomposition of one molecule of 

 sugar into two molecules of lactic acid : C 6 H 12 =2 C 3 H 6 3 ; 

 and for the relation with proteins we may at once refer to 

 the deamidization of alanin: CH 3 .CH(NH 2 ).COOH + 

 H 2 = NH 3 + CH 3 .CH(OH).COOH. (The possibility of 

 an actual intracorporeal transformation of alanin into lactic 

 acid has been demonstrated by the experiments of Neuberg 

 and Langstein upon animals deprived of glycogen.) 



We may first take up for consideration the postmortem 

 acid change of the tissues. The fact has been known a very 

 long time that this is due to formation of lactic acid, and 

 that the much studied postmortem production of acid in 

 muscle (Vol. I of this series, pp. 145-147, Chemistry of the 

 Tissues) is nothing more than a particular instance of a 

 process equally likely to occur in all the tissues. This acid 

 change is at present regarded as a continuation of an intra- 

 vital process. A great number of investigations have been 

 devoted to the subject of acid production in aseptic and anti- 



8 J. H. Ryffel, Jour, of Physiol., 39, Proc. Physiol. Soc., V, 1909. 



