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LACTIC ACIDS. 583
in poisoning by phosphorus, and especially after extirpation of the liver
seems to be paralactic acid.
The origin of paralactic acid in the animal organism has been sought
by several investigators, who took for basis the researches of Gaglio,
Minkowski, and Araki, in a decomposition of protein in the tissues
Gaglio claims a lactic-acid formation by passing blood through the sur-
viving kidneys and lungs. He also found 0.3-0.5 p. m. lactic acid in the
blood of a dog after protein food, and only 0.17-0.21 p. m. after fast-
ing for forty-eight hours. According to Minkowski the quantity of lactic
acid eliminated by the urine in animals with extirpated livers is increased
with protein food, while the administration of carbohydrates has no
effect. Araki has also shown that if we produce a scarcity of oxygen
in animals (dogs, rabbits, and hens) by poisoning with carbon monoxide,
by the inhalation of air deficient in oxygen, or by any other means, a
considerable elimination of lactic acid (besides sugar and also often
albumin) takes place through the urine, an observation which has been
confirmed by Saito and Katsuyama.1
As a scarcity of oxygen, accord-
ing to the ordinary statements, produces an increase of the protein
catabolism in the body, the increased elimination of lactic acid in these
cases must be due in part to an increased protein destruction and in part
to a diminished oxidation.
Araki has not drawn such a conclusion from his experiments, but
he considers the abundant formation of lactic acid to be due to a cleavage
of the sugar formed from the glycogen. He found that in all cases where
lactic acid and sugar appeared in the urine the quantity of glycogen
in the liver and muscles was always diminished. Without denying
the possibility of a formation of lactic acid from protein, he states that
with lack of oxygen we have to deal with an incomplete combustion
of the lactic acid derived by a cleavage of the sugar. Although the
abundant formation of lactic acid under these circumstances can be
explained in different ways, still there are other conditions which make
the formation of lactic acid from proteins very probable. To this
belongs the lactic acid formation from alanine, in the liver, as mentioned
in a previous chapter, and recently further substantiated by Embden
and F. Kraus.2
The carbohydrates are also considered as the mother-substance
of the lactic acid, as it is now generally admitted that the cleavage of the
1
Gaglio, Arch f (Anat. u.) Physiol., 1886; Minkowski , Arch exp. Path, u. Pharm.,
21 and 31; Araki, Zeitschr. f. physiol. Chem., 15, 16, 17, and 19; Saito and Katsuyama.
ibid., 32.
2
Neuberg and Langstein, Arch. f. (Anat. u.) Physiol. 1903; Embden and F. Kraus,
Bioch Zeitschr. 45.
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