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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, CH3.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 ghjoxylase 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.
»See Embden und Oppenheimer, Bioch. Zeitschr., 45; Parnas and Baer, ibid., 41.
2 Yirchow’s Festschrift, also Her. d. deutsch. chem. Gesellsch., 25, Referatb., 685.
3
Simdeek, Centralbl. f. Physiol., 1"; 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.
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