Haughton’s method of estimating Urea from the specific gravity of the Urine. After having measured the urine voided during 24 hours, and determined the specific gravity of the whole collected amount, and then consulting the accompanying table, compiled by Professor Haughton, the number of grains of urea excreted per diem is immediately ascertained. This quantity will be shown by the figures which stand at the points where the lines running respectively from the number of fluid ounces and the ‘specific gravity’ intersect each other. Thus, suppose the daily amount of urine to have been 30 ounces, and the specific gravity 1006, the number of grains of urea contained in it will be 85. This method is inserted for urines containing sugar and albumen.
Determination of the Water. The amount of water in any sample of urine may be determined by weighing 1000 grains of the recently excreted urine into a counterpoised platinum or porcelain dish, and ascertaining the loss it has undergone after evaporation to dryness. The operation should be performed as speedily as possible. The best plan is to concentrate the urine in a water bath, the evaporation should be continued in vacuo over strong sulphuric acid, until the weight of the residue remains constant. By way of control, another sample of the same urine, consisting of 500 grains, may be operated upon at the same time, and under the same conditions.
Urinary Deposits, &c. These differ from the albumen, sugar, bile, &c., previously described, in being insoluble in abnormal
urine. Sometimes they are diffused throughout the whole body of the urine, when they give it an opaque appearance. Sometimes they may be met with floating on its surface; at others they are only partially diffused through the fluid, frequently in the form of a transparent or opaque cloud, when they occupy a considerable space; whilst very often they occur in a crystalline or granular form, deposited sometimes at the bottom and sometimes at the sides of the vessel holding the urine.
Of the numberless insoluble substances met with in urine, both in health and disease, our limits will only permit us to notice those which are most important, and of frequent occurrence.
For the detection of the generality of these the microscope is indispensable. An instrument magnifying 200 to 220 diameters (1⁄4 of inch objective) will generally be found sufficiently powerful, and in some instances an inch objective, magnifying 40 diameters (as in the larger forms of crystalline deposit) will answer all the purposes.
Some of the varieties of these deposits admit of a double examination, viz. a microscopical and chemical one. When this is the case, the particulars applying to each kind of investigation will be given.
Mucus. Mucus is always present in small quantity in healthy urine, in which it shows itself within a few hours after the urine has been excreted in the shape of a transparent cloud towards the bottom of the vessel containing the urine.
Pus. The presence of pus in urine is indicated by an opaque, more or less bulky, cream-like deposit at the bottom of the vessel holding the urine, to which some separated pus globules, finding their way to the supernatant liquid, give an appearance of slight turbidity. By shaking the vessel the whole of the liquid becomes turbid, owing to the equal dissemination through it of the pus globules. The pus again deposits on standing. A small quantity of albumen is always met with in the clear part of urine which contains pus; the albumen being derived from the liquor puris, the liquid by which the pus-corpuscles are surrounded.
Whenever it can be obtained in sufficient quantity, pus should always be examined chemically, as follows:—The supernatant urine being decanted, the suspected sediment is shaken up with liquor potassæ, when if it become converted into a gelatinous, viscid substance, incapable of being dropped from the tube, and when poured from it running as a slimy and almost continuous mass, it may be pronounced pus. This same gelatinous viscid mass is met with in alkaline urines containing pus, adhering to the sides of the vessel in which the urine is placed, where it has been formed by the action of the carbonate of ammonia (caused by the decomposition