584 MUSCLES. 



sugar in the animal body occurs, or at least can occur, with lactic acid as 

 an intermediary step. The views are indeed different 1 as to the closer 

 mechanism of this cleavage, but there does not exist any doubt that a 

 formation of lactic acid, and in fact paralactic acid, can take place from 

 carbohydrates in the animal body. HOPPE-SEYLER 2 held the view that 

 the formation of lactic acid, in the absence of free oxygen, from gly- 

 cogen or glucose was probably a function of all living protoplasm and in 

 the anaerobic metabolism of the animal cells, according to the investiga- 

 tions of STOKLASA 3 and his collaborators on alcoholic fermentation in 

 the tissues, a formation of alcohol and carbon dioxide takes place from 

 the sugar with lactic acid as intermediary step. The correctness of these 

 statements is now disputed from many sides, but we have direct observa- 

 tions which speak positively for a lactic acid formation from glycogen 

 or sugar. Thus EMBDEN 4 and co-workers have found that on transfus- 

 ing blood through the liver rich in glycogen, a formation of lactic acid 

 takes place, and an abundance of lactic acid is formed when blood rich in 

 sugar is transfused through a glycogen free liver, while a blood poor in 

 sugar led only to a very inconsiderable formation of lactic acid. 



Certain investigators (see page 333) admit of the occurrence of glyceric 

 aldehyde (and also dioxyacetone) as intermediary products in the forma- 

 tion of lactic acid from sugar. Another intermediary product in the 

 lactic acid formation has been shown by recent thorough investigations 

 to be methylglyoxal, CHs.CO.CHO. An abundant formation of lactic 

 acid from methylglyoxal has been obtained by certain investigators, 

 such as DAKIN and DUDLEY, and by NEUBERG, in experiments with 

 tissues, organ extracts and organ pulp, and by LEVENE and MEYER 5 in 

 experiments with leucocytes or kidney tissue. The process is of an 

 enzymotic nature and the active enzyme, which also converts phenyl- 

 glyoxal into mandelic acid has been called glyoxylase by DAKIN and 

 DUDLEY. The process is reversible according to these experimenters, 

 in that they have been able to show a retransformation of lactic acid 

 into methylglyoxal. They also found that lactic acid as well as methyl- 

 glyoxal could form glucose in diabetic animals. The detailed procedure 

 in the cleavage of sugar to lactic acid is still undecided. 



The carbohydrates, as well as the proteins, it seems, must be con- 

 sidered as the material from which the lactic acid is formed in the body. 



1 See Embden und Oppenheimer, Bioch. Zeitschr., 45; Parnas and Baer, ibid., 41. 

 2 Virchow's Festschrift, also Eer. d. deutsch. chem. Gesellsch., 25, Referatb., 685. 

 3 Simdcek, Centralbl. f. Physiol., 17; Stoklasa, Jelinek, and Cerny, ibid., 16. In 

 regard to opposed statements see Harden and Mac Lean, Journ. of Physiol., 42. 



4 Embden and Almagia with F. Kraus, Bioch. Zeitschr. 45; S. Oppenheimer, ibid., 45. 



5 Dakin and Dudley, Journ. of biol. Chem., 14; Neuberg, Bioch. Zeitschr., 49; 

 Levene and Meyer, Journ. of biol. Chem., 14. 



