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894 METABOLISM.
In man and also in animals sometimes a rise in the nitrogen excretion
is observed about the second or third starvation day, which is then fol-
lowed by a regular diminution. This rise is explained by Prausnitz,
Tigerstedt, Landergren,1
as follows: At the commencement of star-
vation the protein metabolism is reduced by the glycogen still present
in the body. After the consumption of the glycogen, which takes place
in great part during the first days of starvation, the destruction of pro-
teins increases as the glycogen action decreases, and then decreases again
when the body has become poorer in available proteins.
Other conditions, such as varying quantities of fat in the body, have
an influence on the rapidity with which the nitrogen is eliminated during
the first days of starvation. After the first few days of starvation the
elimination of nitrogen is more uniform. It may diminish gradually
and regularly until the death of the animals or there may be a rise in the
last days, a so-called premortal increase. Whether the one or the other
occurs depends upon the relation between the protein and fat content
of the body.
Like the destruction of proteins during starvation, the decomposi-
tion of fat proceeds uninterruptedly, and the greatest part of the’ calories
needed during starvation are supplied by the fats. According to Rubner
and Voit the protein catabolism varies only slightly in starving animals
at rest and at an average temperature, and forms a constant portion
of the total exchange of energy; of the total calories in dogs 10-16 per
cent comes from the protein decomposition and 84-90 per cent from the
fats. This is at least true for starving animals which had a sufficiently
great original fat content. If on account of starvation the animal has
become relatively poorer in fat and the fat content of the body has fallen
below a certain limit, then in order to supply the calories necessary, a
larger quantity of protein is destroyed and the premortal increase now
occurs (E. Voit). The reason for this premortal rise in protein catabol-
ism is still not completely understood (Schulz and collaborators 2
).
Since the fat has a diminishing influence on the destruction of pro-
teins corresponding to what was said above, the elimination of nitrogen
in starvation is less in fat than in lean individuals. For instance, only
9 grams of urea were voided in twenty-four hours during the later stages
of starvation by a well-nourished and fat person suffering from disease
of the brain, while I. Munk found that 20-29 grams urea were voided
daily by Cetti,3 who had been poorly nourished.
’Prausnitz, Zeitsohr. f. Biologie, 29; Tigerstedt and collaborators, 1. c; Landergren,
Undersokningar ofver menniskans agghviteomsattning, Inaug.-Diss. Stockholm,.
1902.
2
Voit, Zeitschr. f. Biologie, 41; 167 and 502. See also Kaufmann, ibid., and N_
Schulz, ibid., and Pflu^-r’s Arch., 76, with Mangold, Stubel and Hempel, ibid., 114.
» Berl. klin. Wochenschr., J887.
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