URINARY SEDIMENTS. 197 



UKINAKY SEDIMENTS. 



Besides the soluble constituents of the urine, there 

 are others which appear as an insoluble deposit upon the 

 bottom of the containing vessel or floating in the liquid. 

 They may be present in the freshly-passed urine or may 

 appear after a time. The former are the more important 

 to the physician, although some conclusions as to the con- 

 dition of the system may be drawn from the latter. 



For the collection of these sediments the best method 

 is by the centrifugal machine, or centrifuge, this requir- 

 ing so little time that the examination can be made before 

 changes have occurred in any of the constituents. The 

 centrifugal machine is essentially an apparatus where 

 tubes or other vessels can be set in rapid rotation. These 

 tubes swing from their upper end, and as the speed is 

 increased assume a horizontal position. The solid con- 

 stituents, being heavier than the liquid, are carried by the 

 centrifugal force to the bottom of the tube. The tubes 

 should contain from 15 to 20 cubic centimeters, and be 

 rotated three to five minutes at a speed of at least 1500 

 revolutions per minute. 



If a centrifugal apparatus is not at hand, the sedi- 

 ment is best collected by allowing the urine to stand in 

 a conical glass vessel, containing 4 to 6 fluidounces, until 

 it has settled. Then decant the supernatant liquid or 

 take, by means of a pipette, a sample of the sediment for 

 testing. 



Urinary sediments can be divided into two groups: 

 the organized or anatomical and the unorganized or 

 chemical sediments. Those of the first group are formed 

 by vital processes, and of the latter by chemical force. 



