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788 URINE.
milligrams per liter. Frequently traces of a substance similar to a
nucleoalbumin, which is easily mistaken for mucin, and whose nature
will be treated of later, appears in the urine. In diseased conditions
proteid occurs in the urine in a variety of cases. The albuminous bodies
which most often occur are serglobulin and seralbumin. Proteoses (or
peptones) are also sometimes present. The quantity of proteid in the
urine is in most cases less than 5 p.m., rarely 10 p. m., and only very rarely
does it amount to 50 p. m. or over. Cases are known, however, where it
was even more than 80 p. m.
Among the many reactions proposed for the detection of proteid in
urine, the following are to be recommended:
The Heat Test. Filter the urine and test its reaction. An acid
urine may, as a rule, be boiled without further treatment, and only in
especially acid urines is it necessary to first treat with a little alkali.
An alkaline urine is made neutral or faintly acid before heating. If the
urine is poor in salts, add 1/10 vol. of a saturated common-salt solution
before boiling; then heat to the boiling-point, and if no precipitation,
cloudiness, or opalescence appears, the urine in question contains no
coagulable proteid, but it may contain proteoses or peptones. If a pre-
cipitate is produced on boiling, this may consist of proteid, or of earthy
phosphates,1
or of both. The monohydrogen calcium phosphate decom-
poses on boiling, and the normal phosphate may separate out. The
proper amount of acid is now added to the urine, so as to prevent any
mistake caused by the presence of earthy phosphates, and to give a better
and more flocculent precipitate of the proteid. If acetic acid is used
for this, then add 1-3 drops of a 25 per cent acid to each 10 cc. of the
urine and boil after the addition of each drop. On using nitric acid,
add 1-2 drops of the 25 per cent acid to each cubic centimeter of the
boiling-hot urine.
On using acetic acid, when the quantity of proteid is very small,
and especially when the urine was originally alkaline, the proteid may
sometimes remain in solution on the addition of the above quantity of
acid. If, on the contrary, less acid is added, the precipitate of calcium
phosphate, which forms in amphoteric or faintly acid urines, is liable
not to dissolve completely, and this may cause it to be mistaken for a
proteid precipitate. If nitric acid is used for the heat test, the fact must
not be overlooked that after the addition of only a little acid a combina-
tion between it and the proteid is formed which is soluble on boiling and
which is only precipitated by an excess of the acid. On this account the
large quantity of nitric acid, as suggested above, must be added, but in
this case a small part of the proteid is liable to be dissolved by the excess
of the nitric acid. When the acid is added after boiling, which is absolutely
necessary, the liability of a mistake is not so great. It is on these grounds
that the heat test, although it gives very good results in the hands of
experts, is not recommended to physicians as a positive test for proteid.
1
In regard to the cause of the phosphate precipitation on boiling the urine, see
Malfatti, Hofrneister’s Beitriige, 8.
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