390 THE URINE. 



turbidity produced by boiling is moderate in amount, it may resemble 

 that due to the precipitation of the earthy phosphates. It can, how- 

 ever, be distinguished by the addition of a drop of free acid, which at 

 once redissolves the earthy phosphates, while it does not affect a tur- 

 bidity caused by albumen. An albuminous precipitate, on the contrary, 

 however abundant, is redissolved by the addition of a caustic alkali. 



If the urine be alkaline in reaction, boiling may not throw down the 

 albumen present, this substance being soluble in an alkali. Urine, 

 accordingly, which is suspected of being albuminous, should be first 

 rendered distinctly acid in reaction, if necessary, by the addition of a 

 small quantity of acetic acid. 



Nitric acid, added to albuminous urine, produces a turbidity by 

 coagulation of the albumen. Alcohol, added to the urine in equal 

 volume, will have the same effect ; and a solution of potassium ferrocy- 

 anide, acidulated with acetic acid, will also produce coagulation. All 

 the above tests, if applied in succession, will leave no doubt as to the 

 presence or absence of albumen. 



Deposits in the Urine. 



The deposits which appear spontaneously in the urine consist either : 

 1st, of some of its normal ingredients, thrown down in consequence 

 of a disturbance in its relative composition; or 2d, of exudations 

 from the mucous membrane of the urinary passages, owing to a dis- 

 eased condition of the parts. Those belonging to the first class are the 

 earthy phosphates and the urates. The most common of those belong- 

 ing to the second are blood, mucus, and pus. 



Deposits of the Earthy Phosphates, These deposits are always of a 

 white color, and are seldom abundant. When the urine is first passed, 

 the phosphates are disseminated through its mass in the form of a light 

 cloudiness, which settles slowly to the bottom of the vessel. The 

 urine is alkaline or neutral in reaction, and is usually of less than the 

 average specific gravity. The precipitate is amorphous, presenting no 

 crystalline forms under the microscope. It is at once redissolved on 

 the addition of an acid, and presents all the chemical reactions which 

 have been described as belonging to the earthy phosphates. The alka- 

 line reaction of the urine, which gives rise to the appearance of this 

 deposit, may be due to a temporary diminution in the quantity of uric 

 acid produced in the system, or to an unusual formation of alkaline 

 carbonates from the use of fruits or vegetables containing salts of the 

 vegetable acids. 



Deposits of the Urates. The urates appear as a deposit when the 

 formation of uric acid in the system is unusually abundant in propor- 

 tion to the entire quantity of the urine, so that a portion of the urates 

 are no longer held in solution. The urine is nearly always concentrated, 

 highly colored, above the average specific gravity, and of a strongly 

 acid reaction. The deposit is sometimes nearly white, but usually it is 

 of a light pink or even red color, according to the degree of concentra- 



