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762 UKINE.
phoric acid. The total quantity of phosphoric acid varies and depends on
the character and the quantity of food. The average quantity of P2O5
is in round numbers 2.5 grams, with a variation of 1-5 grams per day.
A small part of the phosphoric acid of the urine originates from the
burning of organic compounds, such as nuclein, and phosphatides
within the organism; on exclusive feeding with substances rich in nuclein
or pseudonuclein the quantity of phosphates is essentially increased;
still it is undecided to what extent the excretion of phosphoric acid is
a measure of the absorption and decomposition of these bodies.1
The
greater part originates from the phosphates of the food, and the quan-
tity of phosphoric acid eliminated is greater when the food is rich in
alkali phosphates in proportion to the quantity of lime and magnesium
phosphates. If the food contains much lime and magnesia, large quan-
tities of earthy phosphates are eliminated by the excrement; and even
though the food contains considerable amounts of phosphoric acid in these
cases, the quantity excreted by the urine is small. This is especially
true of herbivora, in which the kidneys are the chief organs for the
excretion of alkali phosphates. In man, according to Ehrstrom, the
content of lime in the food seems to play no important role, as in his exper-
iments about one-half of the phosphoric acid taken as CaHP04 was
absorbed, still the extent of phosphoric-acid excretion through the urine
depends in man not only upon the total quantity of phosphoric acid in
the food, but also upon the relative amounts of the alkaline earths and the
alkali salts of the food. In carnivora, in which phosphate injected sub-
cutaneously is eliminated by the intestine (Bergmann), the urine is
habitually poor in phosphates.2
As the extent of the elimination of phosphoric acid is mostly dependent
upon the character of the food and the absorption of the phosphates
in the intestine, it is apparent that the relation between the nitrogen and
phosphoric-acid excretion cannot run parallel. This is in fact so, and,
according to Ehrstrom, the organism has the power of accumulating
large quantities of phosphorus for a relatively long time independent of
the condition of the nitrogen balance. With a certain regular food the
relation between nitrogen and phosphoric acid in the urine can be kept
almost constant. Thus on feeding with an exclusive meat diet, as
observed by Voit 3 in dogs, when the nitrogen and phosphoric acid
1
See A. Gumlich, Zeitschr. f. physiol. Chem., 18; Roos, ibid., 21; Weintraud,
Arch. f. (Anat. u.) Physiol., 1895; Milroy and Malcolm, Journ. of Physiol., 23; Roh-
mann and Steinitz, Pfluger’s Arch., 72; Loewi, Arch. f. exp. Path. u. Pharm., 44 and 45.
2
Ehrstrom, Skand. Arch. f. Physiol., 14; Bergmann, Arch. f. exp. Path. u. Pharm.,
47.
3
Physiologie des allgemeinen Stoffwechsels und der Ernahrung in L. Hermann’s
Handbuch, (J, Thill. 1, 7’.).
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