INORGANIC CONSTITUENTS OF URINE. 697 



Urinary deposits may be preserved either in the dry way, in 

 Canada balsam, turpentine, oil, and similar fluids, or in aqueous 

 solutions. Only large crystals of the oxalate of lime, lithic acid, 

 and some of the phosphates and lithates, can be preserved in the 

 dry way. Dr. Beale gives the following directions for the pre- 

 servation of urinary deposits: "After the crystals have been 

 allowed to collect at the bottom of a conical glass vessel, the 

 clear supernatant fluid is to be poured oflj and the crystals are to 

 be washed with a little dilute alcohol, or with a very weak solu- 

 tion of acetic acid. "When the process of washing has been re- 

 peated two or three times, a small quantity of the deposit is to 

 be transferred by means of a pipette to a glass slide, and the 

 greater part of the fluid soaked up with a small piece of blotting 

 paper. The crystals are next to be spread a little over the glass 

 with the aid of a fine needle, in order to separate the individual 

 crystals from each other ; and the slide is to be placed in a warm 

 place, or in the sun, until quite dry; but care must be taken that 

 the drying is not carried on too rapidly, and that too great a 

 degree of heat is not employed. A narrow rim of paper, or card- 

 board, is next to be gummed on the slide so as to include the 

 crystals in a sort of shallow cell; and lastly, the glass cover is to 

 be put on and kept in its place either by anointing the edges with 

 a little gum-water, or by pasting it down with narrow strips of 

 paper, which may be variously arranged and ornamented accord- 

 ing to taste. 



"If the crystals of lithic acid are to be mounted in Canada 

 balsam, they should be carefully dried first, as above directed, 

 and afterwards over sulphuric acid, and then moistened with a 

 small drop of spirits of turpentine. The slide is now to be 

 slightly warmed, in order to volatilize the greater part of the 

 turpentine, and a drop of Canada balsam is to be dropped upon 

 the preparation from the end of a wire, which may be readily 

 eftected by holding the wire with the balsam over the lamp or 

 hot brass plate for a minute or two in order to soften it. The 

 slide is next to be held over a lamp, in order to keep the balsam 

 fluid until any air-bubbles which may be present have collected 

 into one spot on the surface of the liquid balsam, an operation 

 which is expedited by gently moving the slide from side to side. 

 The air-bubbles may now be removed by touching them with a 

 fine-pointed wire. Lastly, the glass cover is to be taken up with 

 a pair of forceps, slightly warmed over a lamp, and one edge is 

 allowed to touch the balsam. The surface is permitted to fall 

 gradually upon the balsam, so that it is wetted by it regularly, 

 and only by very slow degrees, for otherwise air-bubbles would 

 yet be included in the preparation. The glass slide with the pre- 

 paration may now be set aside to cool." 



There are many substances, however, which cannot be pre- 

 served to advantage in Canada balsam, or by the dry method. 

 Such are epithelium, casts, torulse, confervse, fat-cells, pus, mucus, 

 &c. Such substances should be placed in shallow glass-cells, 



