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METABOLISM WITH FOOD RICH IX PROTEINS. 909
proteins, are ordinarily catabolized to only a small extent, about 1 per
cent daily (Voit). By an increased supply of proteins the activity of
the cells and their ability to decompose nutritive proteins is also increased
to a certain degree. When nitrogenous equilibrium is obtained after
an increased supply of proteins, it indicates that the decomposing power
of the cells for proteins has increased so that the same quantity of proteins
is metabolized as is supplied to the body. If the protein metabolism is
decreased by the simultaneous administration of other non-nitrogenous
foods (see below), a part of the circulating proteins may have time to
become fixed and organized by the tissues, and in this way the mass of
the flesh of the body increases. During starvation or with a lack of pro-
teins in the food the reverse takes place, for a part of the tissue protein-
is converted into circulating proteins which are metabolized, and in this
case the flesh of the body decreases.
Voit’s theory has been criticised by several investigators and espe-
cially by Pfluger. Pfluger’s belief, based on an investigation made
by one of his pupils, Schondorff, 1
is that the extent of protein destruc-
tion is not dependent upon the quantity of circulating proteins, but
upon the nutritive condition of the cells for the time being—a view
which does not widely differ from Voit if the author does not misunder-
stand Pfluger. Voit 2
has, as is known, stated that the conditions f < >r
the destruction of substances in the body exist in the cells, and also that
the circulating protein is first catabolized after having beon taken up
by the cells from the fluids washing them. Besides this, certain inves-
tigations conclusively show that the extent of protein catabolism is depend-
ent upon the concentration of the decomposable proteins at the place
where the decomposition is taking place. Thus in confirmation with
the earlier investigations of v. Gebhardt and Krummacher, Thomas,
v. Hoesslin and Lesser 3
have recently shown that on feeding with
a certain quantity of protein, less protein was catabolized when the pro-
tein was supplied piecemeal, i.e., in several small portions during the day
instead of at one time. That the peculiarity of the nitrogen elimination
in starvation and after sufficient protein supply depends essentially
upon the concentration of the decomposable proteins (or more correctly the
decomposable nitrogenous substances) is no doubt also generally admitted.4
1
Pfluger, Pfluger’s Arch., 54; Schondorff, ibid., 54.
2
Zeitschr. f. Biologie, 11.
3
K. Thomas. Arch. f. (Anat. u.) Physiol., 1909; H. v. Hoesslin and E. J. Lesser,
Zci schr. f. physiol. Chem., 73, when also the works of v. Gebhardt and Kummacher are
cited.
4
See also E. Voit and A. Korkunoff, Zeitschr. f. Biol., 32, and O. Frank and R.
Trommsdorff, ibid., 43.
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