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39G THE LIVER.
be inverted in the intestine. These two varieties of sugar, therefore,
cannot, like glucose and fructose, serve as glycogen-formers after sub-
cutaneous injection, but reappear almost entirely in the urine (Dastre,
Fr. Voit). Maltose, which is inverted by an enzyme present in the blood,
passes only to a slight extent into the urine (Dastre and Bourquelot
and others), and it can, like the monosaccharides, even after subcuta-
neous injection, be used in the formation of glycogen (Fr. Voit).1
Of
the disaccharides the maltose and the cane-sugar are strong glycogen-
formers while milk-sugar has only a weak action.
The ability of the liver to form glycogen from monosaccharides has
also been shown by K. Grube in a very interesting and direct manner,
by perfusion experiments with solutions of various carbohydrates. In
these perfusion experiments on tortoise livers, glucose produced an
abundant glycogen formation, while with fructose and galactose it was
less abundant. Pentoses, disaccharides, casein and amino-acids (gly-
cocoll, alanine and leucine) were inactive while on the contrary glycerin
and also formaldehyde acted as glycogen-formers. The formation of
glycogen from formaldehyde is disputed by Schondorff and Grube.2
After Pavy 3 first showed the occurrence of carbohydrate groups in
ovalbumin, other investigators were able to split off glucosamine from
this and other protein substances (see Chapter II), and the question
arose whether the amino-sugar could serve in the formation of glycogen.
The investigations carried out in this direction by Fabian, Frankel
and Offer, Cathcart and Bial, have shown that the glucosamine
introduced into the organism is in part eliminated unchanged in the
urine and has no glycogen-forming action. No definite conclusions
can be drawn from this on the behavior of the carbohydrate groups,
which exist not as free groups but combined with the protein molecules.
The investigations of Forschbach on the behavior of glucosamine
chained to an acid-group in an amide-like combination, as well as the
investigations of Kurt Meyer and Stolte,4
have yielded no proofs for
the theory that glycogen is formed from glucosamine.
Whether or not, or to what extent, the glucoproteins by their glucosa-
mine component take part in the sugar or glycogen formation in the animal
’Dastre, Arch, de Physiol. (5) 3, 1891; Dastre and Bourquelot, Compt. Rend., 98;
Fritz Voit, Verhandl. d. Gesellsch. f. Morph. u. Physiol, in Miinchen, 1896, and Deutsch.
Arch. f. klin. Med., 58. In regard to the glycogen formation after intravenous injection
of sugar see Freund and Popper, Bioch. Zeitschr., 41.
2
Pfluger’s Arch., 138; Grube, ibid., 118, 121, 122, 126 and 139.
3
The Physiology of the Carbohydrates, London, 1894.
* Fabian, Zeitschr. f. physiol. Chem., 27; Frankel and Offer, Centralbl. f. Physiol.,
13; Cathcart, Zeitschr. f. physiol. Chem., 39; Bial, Berl. klin. Wochenschr., 1905;
Forschbach, Hofmeister’s Beitrage, 8; Meyer, ibid., 9; Stolte, ibid., 11.
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