rino in a solution of stannous chloride, and dry in a water-bath. On moistening one of these strips with diabetic urine, and holding it near the fire, a brownishblack color results.

6. Fermentation Test.-Ordinary yeast is mixed with water, and a long test-tube filled with the suspected urine, to which some of the yeast has been added. Invert the tube over a saucer containing the urine under examination, so that no air may enter, and set the whole aside in a warm place. Sugar, if present, will be decomposed into carbonic acid and alcohol, and the gas will collect in the upper part of the tube. Or the carbonic acid may be conducted off by a fine tube into lime water, which be comes turbid from the formation of insoluble carbonate of lime.

BILE. Urine containing bile has a peculiar greenishblack color.

The tests are the following:

1. Noel's Test.-Immerse a strip of blotting paper for a few minutes in the fluid, dry, and add a drop of nitric acid containing a little nitrous acid. If bile be present, a violet color results, changing to red or yellow.

2. Pettenkofer's Test for Bile Acids.—Add to the liquid, in a test-tube, a little powdered white sugar, or its equiv alent of syrup. Then pour in of strong sulphuric acid (very gradually) rather more than half the bulk of the liquid. The temperature is thus gradually raised to the proper point, and a deep purplish-crimson color appears. This test frequently fails in the examination of the urine.

3. Nitric Acid Test.-Place a drop of the fluid on a white porcelain plate, add carefully a drop or two of strong nitric acid, and at the point of contact of the fluid with the acid there will be a play of colors, passing from red to green, pink, blue, violet, and yellow. The green

tinge, though often evanescent, indicates the presence of bile.

4. Oxide of Silver Test.-Boil the fluid with an ammoniacal solution of silver oxide. Acidulate the filtrate with a few drops of hydrochloric acid. If biliverdin be present, a purple color will be produced, owing to the formation of an artificial compound, bilipurpin.

5. Maréchal's Test.-This is employed as follows: Place about 3j of the urine in a test-tube, and allow one or two drops of tincture of iodine to trickle down the side of the tube, held nearly horizontally, so that the two fluids may touch, but not mix. If bile pigment be present, a fine green color will almost immediately be developed below the red iodine layer. By holding the test-tube up against a white cloud, or a white surface, in a good light, the three zones of color will be distinctly visible.1

LACTIC ACID. This acid is rarely present in the urine, but may be detected by evaporating fresh urine nearly to dryness, and treating the residue with a solution of oxalic acid in alcohol. Oxalates are precipitated; lactic acid remains in solution, which is digested with litharge, evaporated to dryness, and an alcoholic solution of lactate of lead obtained, which is decomposed by sulphuretted hydrogen, the sulphide of lead filtered off, and the fluid evaporated to a syrup. The syrup is then shaken up with ether, the ethereal solution evaporated, and the lactic acid dissolved in water. The aqueous solution is then boiled with zinc oxide, and the crystals of lactate of zinc are allowed to separate.

Of the other abnormal constituents, FAT, in the form. of oil globules, usually associated with fatty casts, may indicate an advanced condition of Bright's disease.

Dr. W. G. Smith, Dub. Journ. Med. Science, Dec. 1876, in Amer. Journ. Med. Sciences, April, 1877, 531.

CHYLE gives a white appearance to the urine, from the abundance of fatty molecules it contains; albumen is sometimes present when it coagulates on cooling. Possibly there may be abnormal communication between the lacteal system and the ureters or kidneys.-KIESTEIN, a granular albuminous matter, occurs in the urine of pregnant women, forming with crystals of triple phosphate and fat globules a fat-like scum on the surface.-ACETIC and BUTYRIC ACIDS are found only in decomposing urine, and are not important.-SULPHURETTED HYDROGEN is rarely found in urine, but may be detected by blackening a piece of paper dipped in a solution of acetate of lead and held over it.—ALLANTOIN is only a temporary and occasional constituent, in young children especially.-LEUCIN occurs in hepatic cases, and is detected by microscopic examination. It is usually seen in roundish yellowishcolored balls, made up of masses of small needle-like crystals. TYROSIN occurs under similar conditions, and is similarly detected, consisting of stellate groups of long silky needles, not in balls or colored, as with leucin.

Examination of the Sediments of Urine.

Urinary deposits may be divided into three classes: 1. Those which occur in acid or alkaline urine, namely, uric acid, urates, phosphates, oxalates, and cystin. 2. In alkaline urine only, namely, the ammoniaco-magnesian, or triple phosphate, phosphate of lime, and urate of ammonia. 3. Organized deposits, namely, mucus, blood, pus, tube casts, spermatozoids, torulæ, sarcina, bacteria, vibriones, etc.

I. Deposits found occasionally in Acid or Alkaline Urine, usually in the former.

URIC ACID.-Yellow, reddish, or brown sediment; little masses of crystals, assuming various forms, as lozenge

shaped rhombs, rectangular tables or prisms, dumb-bell and spindle or barrel-shaped crystals.

Urates. These appear when the urine is cold, if the salts are present in excess, the urates being much more. soluble in hot water than in cold. Consequently every deposit which disappears on heating consists of urates. They usually form a heavy precipitate at the bottom of the glass, with an ill-defined upper border; and are white or deeply tinted by the coloring matter of the urine. They have been termed "lateritious deposit," "brick-dust deposit," "critical deposit," and "purpurates."

Urate of soda is amorphous in urine, but prepared artificially by acting with uric acid on sodium phosphate, it forms acicular crystals.

Urate of ammonia appears as an amorphous granular sediment, or in the form of brown round balls covered with spines.

Urate of lime is a white amorphous powder, of rare

Occurrence.

PHOSPHATES. In acid urine they appear as a cloudy precipitate, at once soluble in a drop of nitric or hydrochloric acids.

OXALATE OF LIME may be detected by its characteristic octahedral or dumb-bell crystals. It is not a distinct sediment, but exists as isolated crystals entangled in the mucous cloud with which it is usually associated.

CYSTIN. This occasionally exists as a sediment mixed with amorphous urates. Under the microscope it is seen in transparent, colorless, six-sided plates. If it occurs in large quantity along with urates or phosphates, or both, it may be distinguished from them by heating and adding acetic acid; the heating dissolving the urates, and the acid the phosphates, but neither have any effect on the cystin.

II. Deposits found occasionally in Alkaline Urine only.

When, from any cause urine becomes alkaline, from the decomposition of urea into carbonate of ammonia, the earthy phosphates (of lime and magnesia), which are soluble only in a slightly acid fluid, are at once thrown down; the phosphate of lime remains unchanged, but the ammonia unites with the phosphate of magnesia and forms a precipitate of ammoniaco-phosphate of magneśia, or triple phosphate.1

The deposits of this class are all dissolved on adding a few drops of nitric or hydrochloric acid.

AMMONIACO MAGNESIAN, OR TRIPLE PHOSPHATE.-It usually occurs in six-sided crystals, some elongated, others nearly square, some with sharp angles, others with broad facets. In very alkaline urine, they appear as feathery crystals.

PHOSPHATE OF LIME.-Usually an amorphous white powder; occasionally, aggregated into rosette-like crystals.

URATE OF AMMONIA and URATE OF LIME, already referred to, may also be present; the former always in alkaline, rarely in acid urine; the latter occasionally in alkaline urine.

III. Organized Deposits.

MUCUS. The cloudy transparent flocculi seen in urine, when left at rest, consist of mucus entangling various forms of epithelial cells, derived from the urinary pas sages. The supernatant liquid being carefully poured. off, and acetic acid added to the mucus, it coagulates, forming delicate molecular fibres.

1 Neubauer and Vogel. Guide to Qualitative and Quantitative Analysis of the Urine. (New Sydenham Society's Publications.) 4th ed., p. 56.