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GLYCOGEN FORMERS. 393
tion, as suggested by BrxJcke, it is better, for quantitative determinations
of glycogen, to precipitate it directly from the alkaline solution by alcohol
(Pfluger 1
).
The quantitative estimation is best performed according to Pfluger’s
method, which is as follows: The finely divided organ is heated on
the water-bath for 2-3 hours in the presence of 30 per cent KOH; after
diluting with water and filtering, the glycogen is precipitated with
alcohol, and the redissolved glycogen estimated in part by the polar-
iscope and in part as sugar after inversion. One part by weight of sugar
equals 0.927 part glycogen. As in the estimation the prescribed direc-
tions must be exactly followed, we must refer to the original work of
Pfluger for the details of the method. Other methods of estimating
glycogen, such as those of Brucke-Kulz, Pavy, and Austin, are described
in Pfluger’s Archiv. 96. Also compare the recent works of Pfluger.2
Numerous investigators have endeavored to determine the origin
of glycogen in the animal body. It is positively established by the
unanimous observations of many investigators 3
that the varieties of
sugars and their anhydrides, dextrins and starches, have the property of
increasing the quantity of glycogen in the body. The action of inulin
seems to be somewhat uncertain.4
The statements are questioned in
regard to the action of the pentoses. Cremer found that in rabbits and
hens various pentoses, such as rhamnose, xylose, and arabinose, have a
positive influence on the glycogen formation, and Salkowski obtained
the same result on feeding /-arabinose. Frentzel, on the contrary,
found no glycogen formation on feeding xylose to a rabbit which had
previously been made glycogen-free by strychnine poisoning, and Neu-
berg and Wohlgemuth 5
obtained similar negative results on feed-
ing rabbits with d- and r-arabinose. In general we can for the present
accept the view that the pentoses are not direct glycogen formers.
The hexoses, and the carbohydrates derived therefrom, do not all
possess the ability cf forming or accumulating glycogen to the same
extent. Thus C. Voir 6
and his pupils have shown that glucose has a
more powerful action than cane-sugar, while milk-sugar is less active
(in rabbits and hens) than glucose, fructose, cane-sugar, or maltose.
The following substances when introduced into the body also increase the
quantity of glycogen in the liver: Glycerin, gelatin, arbutin, and likewise, accord-
*See also the method suggested by Gautier, Compt. Rend., 129.
2
Pfluger’s Arch., 103, 104, 121 and especially 129.
J
In reference to the literature on this subject, see E. Kiilz, Pfluger’s Arch., 24,
and Ludwig, Festschrift, 1891; also the cited works of Pfluger and Cremer, foot-note
2, p. 390.
* See Miura, Zeitschr. f. Biologie, 32, and Nakaseko, Amer. Journ. of Physiol., 4.
6
Salkowski, Zeitschr. f. physiol. Chem., 32; Neuberg and Wohlgemuth, ibid., 35.
See also Pfluger, 1. c, and Cremer, 1. c.
6
Zeitschr. f. Biologie, 28.
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