HISTOLOGICAL DEMONSTRATIONS. 123 



URINARY DEPOSITS. 

 The various forms of these are studied in the chemical 



division of the class of Practical Physiology. It is con- 

 venient, however, to study here the methods of mounting 

 them, in order that the student may prepare specimens 

 similar to those which he will afterwards be shown. 



215. Collection and Examination. Allow the urine 

 to deposit in a conical glass, and remove, with the aid of a 

 long pipette, a portion of the sediment for microscopical 

 examination, or remove the supernatant fluid with a syphon, 

 in order that the deposit may not be diffused through the 

 fluid by the disturbing influence of the pipette. For the 

 ordinary examination of the deposit it is generally con- 

 venient to place a drop of the urine on a slide with a 

 shallow cell. The best cell for this purpose, consists of a 

 rounded shallow cavity ground in the centre of the surface 

 of the slide. A cell made of a thin ring of dammar varnish, 

 allowed to dry, also answers the purpose. The cell pre- 

 vents the diffusion of the deposit under the weight of the 

 cover-glass. A magnifying power of 250 is most suitable. 

 Those who employ Hartnack's microscope, with the No. 7 

 objective and No. 3 ocular, should shorten the tube fully, 

 as the power is a little too high with the tube elongated 

 that is to say, the lens requires, in the latter case, to come 

 so near the cover-glass that the whole depth of the cell is 

 not visible. 



216. Mounting. The deposit should be washed at 

 least twice with the fluid in which it is to be mounted, or in 

 rectified spirit in the case of such deposits as uric acid, etc., 

 when they are to be mounted in dammar or Canada balsam. 

 For this purpose allow the urine to deposit. Remove the 

 supernatant fluid with a syphon, or decant it ; pour on the 

 preservative fluid ; allow deposit to form ; remove fluid with 

 a syphon or a pipette, again -pour on preservative fluid, and 

 keep the mixture until wanted. When deposits are to be 

 mounted in fluid media they should always be placed in a shal- 

 low dammar or balsam cell, made by painting a ring of fluid 

 dammar, or Canada balsam, on a slide. With the aid of a 



