1813.] Chemical Properties of Animal Fluids. 41 i> 



B. The Deposit from Urine. 



Urine, by cooling, affords a deposit which varies considerably 

 in different circumstances, not only in quantity, but also in 

 external characters. 'When it is abundant the urine becomes 

 turbid throughout, a grey powder is precipitated, and after con- 

 tinuing for some time at rest, the precipitate is found at the 

 bottom covered with a mucous stratum. The deposit gradually 

 acquires a red tinge, and after some time is found perfectly 

 crystallized. When the urine does not become tuibid, there 

 only appears a thin cloud scarcely discernible, which by rest 

 sinks to the bottom or collects in light transparent flocculi, in 

 which there are sometimes formed, after 24 hours, red crystals. 



All urine, when newly evacuated, contains a matter suspended 

 in it, which in some degree affects its perfect transparency. 

 This matter is the mucus of the inner coat of the bladder. If 

 the urine, while yet warm, be poured on a filter, it will pais 

 perfectly clear, and the mucus will remain on the filter in the 

 -form of transparent and colourless flocculi. The deposit which 

 , afterwards takes place in filtered urine is pulverulent, and nowise 

 mucous : which proves that it is from admixture with the mucus 

 of the bladder, that the flocculent appearance, so frequently 

 assumed by the deposit, arises. By drying, the mucus loses its 

 transparency, becomes red, and sometimes has a crystalline 

 aspect, which is owing to the presence of uric acid, the crystals 

 of which have a diameter exceeding the thickness of the dried 

 mucus. 



If a person, after continuing for a long time either in a stand- 

 ing or fitting posture, without much exercising his muscles, 

 should evacuate urine successively in different vessels, the first 

 portions will contain the largest quantity of mucus, the next less, 

 and the succeeding portions none whatever. Tin's arises from 

 the mucus being heavier than the urine, and collecting in the 

 lower part of the reservoir: but if, on the other hand, a person 

 be obliged to remain long on his back, and to evacuate the urine 

 in that position, the lowermost portion does not come away first, 

 and it then frequently happens that the whole of the mucus 

 cannot !<c evacuated, and that a part remains for a long time in 

 the bladder, when, from the disposition of the uric acid to form 

 crystals in the mass of mucus,* the latter becomes a nucleus for 

 the formation of calculus. To this circumstance may be ascribed 



• I have very often observed thai when the urine lm- been evacuated In 

 portions, of which ilie one contained muens, and the oilier was clear, 



rrded no precipitate, while in the former the mucin was fonnd, after la 

 or 24 boon, to contain oomerous red cryitali mejofcon 



Ii would therefore appear that in urine, which does not contain enough of uric 

 ■eld to form a precipitate by c tiling, the presence of mucus favoan 

 ulai waj Us cry stall! z ition. 



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