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412 THE LIVER.
which the sugar was formed. The formation of sugar from protein is
now generally considered as positively proved.
Darin l
has found with experiments with phlorhizinized dogs that
serine, cysteine, proline, ornithine and arginine yield abundant sugar in
glycosuric animals. Valine, leucine, isoleucine, lysine, histidine, phenyl-
alanine and tryptophane gave relatively little sugar or none at all.
The amino-acids with straight chains (with the exception of lysine) give
sugar while those with branched chains do not. Proline is the only
cyclic amino-acid, which yields abundance of sugar. Arginine is the
only one with more than five carbon atoms which yields sugar and the
sugar comes in this case from the ornithine components.
If we assume a formation of sugar from fat, we must differentiate
between the two components of neutral fats, that is, between the glyc-
erin and the fatty acids. A formation of sugar from glycerin can
be considered as proved by the investigations of Cremer, and especially
those of Luthje 2
and in the following we will discuss only the forma-
tion of sugar from the fatty acids.
The formation of sugar from fat seems to occur in the plant king-
dom, and as the chemical processes in the animal and plant life are in
principle the same, it makes the possibility of a sugar formation from
fat very probable. Such an origin of sugar in the animal body is accepted
by many investigators, especially by Pfuuger and several French observ-
ers, among whom we must specially mention Chauveau and Kauf-
mann.3
When food as free from carbohydrate as possible is taken, the quo-
tient D:N is high, i.e., higher than 8, as well as when the quantity of
sugar is so large that it cannot be accounted for by the calculated
protein (and carbohydrate) metabolism, then if the observations are
otherwise free from error we can admit of a formation of sugar from fat.
Several such cases of diabetes in man have been published (Rumpf,
Rosenqvist, Mohr, v. Noorden, Allard, Falta and co-workers and
others), and also in animals (Hartogh and Schumm 4
). Although these
researches are not fully conclusive, still certain of them indicate a prob-
able formation of su«ar from fat. We also have several conditions which
1
Journ. of biol. Chem., 14, 321.
2
Cremer, Sitzungsber. d. Ges. f. Morph. u. Physiol. Munchen, 1902; Luthje, Deutsch.
Arch. f. klin. Med., 80.
3
Kaufmann, Arch. f. Physiol. (5), 8, where Chauveau’s work is cited.
4
Rumpf, Berl. klin. Wochenschr., 1899; Rosenqvist, ibid.; Mohr, ibid., 1901; v.
Noorden, Die Zuckerkrankheit, 3. Aufl. Berlin, 1901; Allard, Arch. f. exp. Path. u.
Pharm., 57; Falta and co-workers, Zeitschr. f. klin. Med., 66; Hartogh and Schumm,
Arch. f. Path. u. Pharm., 45. See also the works of O. Loewi, ibid., 47, and Lusk,
Zeitschr. f. Biologie, 42.
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