higher than strict accuracy would demand.  Their aggregate proportion, however, is, comparatively speaking, so minute that for most medical purposes their presence may be disregarded.  Greater care must be exercised, though, in those instances where such a deoxidizer as chloral hydrate is accidentally present.  In case of doubt, a little washed and pressed yeast should be allowed to stand with the urine for a day or two in a warm place.  Alcoholic fermentation with evolution of carbonic acid gas soon sets in, and the specific gravity of the liquid is lowered considerably.  This reaction points conclusively to the presence of sugar.

Based upon Braun’s potassic picrate test, Dr. G. Johnson has devised a colorimetric process for the estimation of sugar.  On boiling an alkaline solution of that salt with glucose, the former is reduced to deep red-brown picramate, the color of the liquid, of course, varying in intensity according to the proportion of sugar present.  This solution is diluted till it corresponds in tint with a ferric acetate standard, and the percentage of sugar is then readily calculated.  For those who prefer this process the convenient apparatus manufactured by Mr. Cetti, of 36 Brooke street, Holborn, is recommended, who will also furnish full particulars of the test.

ALBUMEN.

Normal urine is free from coagulable proteids, though it is admitted that albumen may sometimes occur in the absence of disease.  It is always highly important, therefore, to determine accurately the presence or absence of this body.  In the relentless malady named after Richard Bright, the urine always contains albumen, and if accompanied by the “casts” of the uriniferous tubules your report may amount to a sentence of certain death.  The tests which we now describe are accurate and easily applied; but reliance should never be placed on any single reaction—­at any rate until the operator has acquired considerable experience.

Galippe’s picric acid test has within the last few years attracted much attention, chiefly through the commendation it has received from Dr. George Johnson.  A saturated solution is prepared by dissolving 140 grains of recrystallized picric acid (carbazotic acid, or, more correctly, trinitrophenol) in 1 pint of water with heat, and decanting the clear solution.  Some of the urine is rendered perfectly bright by filtration—­repeated, if necessary—­through good filtering paper, and to this an equal volume of the picric acid solution is added.  In the presence of albumen a more or less distinct haze is produced, which on heating to the boiling point is rather intensified than otherwise.  Peptones, if present, yield a similar haze, and quinine or other alkaloid a more or less crystalline precipitate; but in both these cases the opalescence is completely dissipated by heat.  Mucin, an important constituent of some urines, is not affected by picric acid, and the test is decidedly one of great value.