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FORMATION OF FATS. 561
poisoning, that we cannot consider the formation of fat as conclusively
proved. The investigations of Lebedeff, Athanasiu, Taylor, Schwalbe
and others, have shown that probably no new formation of fat from
protein took place, but rather a fat migration and that this is actually
the case has been especially shown by Rosenfeld and recently by Shi-
bata [
in a conclusive manner.
Another more direct proof of the formation of fat from proteins
has been given by Hofmann. He experimented with fly-maggots.
A number of these were killed and the quantity of fat determined. The
remainder were allowed to develop in blood whose proportion of fat
had been previously determined, and after a certain time they were killed
and analyzed. He found in them from seven to eleven times as much
fat as was contained in the maggots first analyzed and the blood taken
together. Pfluger 2
has made the objection that a considerable number
of lower fungi develop in the blood under these conditions, in whose
cell-body fats and carbohydrates are formed from the different con-
stituents of the blood and their decomposition products, and that these
serve as food for the maggots.
Weinland 3
has observed the formation of higher non-volatile fatty
acids in the Calliphora larvae when they were rubbed to a homogeneous
paste after the addition of Witte’s peptone. This experiment shows a
formation of fat from protein, but cannot be considered as quite con-
clusive.
As a more convincing proof of fat formation from proteins, the
investigations of Pettenkofer and Voit are often quoted. These
investigators fed dogs with large quantities of meat containing the least
possible proportion of fat, and found all of the nitrogen in the excreta,
but only a part of the carbon. As an explanation of these conditions
it has been assumed that the protein of the organisms splits into a
nitrogenized and a non-nitrogenized part, the former changing into the
nitrogenized final product, urea, and like products, and the other part,
on the contrary, being retained in the organism as fat (Pettenkofer
and Voit).
Pfluger has arrived at the following conclusion by an exhaustive
criticism of Pettenkofer and Voit’s experiments and a careful recal-
culation of their balance-sheet; that these very meritorious invest iga-
1
Bauer, Zeitschr. f. Biologie, 7; Leo, Zeitschr. f. physiol. Chera., 9; Polimanti,
Pfliiger’s Arch., 70; Pfluger, ibid., 51 (literature on the formation of fat from protein)
and 71; Athanasiu, ibid., 74; Taylor, Journ. Exp. Medicine, 4; see also footnote 2,
p. 384; Shibata,Bioch. Zeitschr., 37, which contains the literature; Rosenfeld, Ergebn.
d. Physiol., 1.
2
See Rosenfeld, Fettbildung, Ergebnisse der Physiologie, 1, Abt. 1.
3
Zeitschr. f. Biol., 51 and 52.
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