180 THE MICROSOOPIST. 



noticed), on the addition of ammonia. The crystalline shape 

 of the triple phosphate, however, readily distinguishes it under 

 the microscope from the amorphous particles of phosphate of 

 lime with which it is usually mixed. The earthy phosphates 

 are readily soluble in dilute acids, from which they are pre- 

 cipitated by ammonia. They are insoluble in a solution of 

 potash. 



Urate of Ammonia constitutes one of the most common 

 urinary deposits. It is gradually deposited as the urine cools, 

 in the form of an amorphous precipitate, which, with a high 

 magnifying power, appears to consist of minute rounded par- 

 ticles, occasionally adhering together, frequently mixed with 

 small crystals of uric acid, and occasionally with the earthy 

 phosphates. A deposit of urate of ammonia readily dissolves 

 when the urine containing it is gently warmed, and is preci- 

 pitated again when the liquid cools. (The earthy phosphates 

 and uric acid are nearly as insoluble in hot as cold water.) 



When urate of ammonia is treated with dilute acetic or 

 hydrochloric acid, it is decomposed, and uric acid, is formed. 



Urate of Soda is often met with in the urine of patients 

 taking medicinally the carbonate or other salts of soda. It re- 

 sembles the urate of ammonia in being soluble in hot water, 

 and in most of its chemical characters, but may be generally 

 recognised without difficulty under the microscope, forming 

 minute globular or granular aggregations, with, occasionally, 

 irregular and curved protuberances. 



Fat may be recognised by the particles being minute round 

 globules, with dark and well-defined outlines, which dissolve 

 when agitated with ether. 



Sometimes this substance is mixed with albuminous matter, 

 forming a kind of emulsion, so that no trace of fat can be per- 

 ceived with the microscope. In such cases, the urine may be 

 agitated with a little ether, which will dissolve the fat, and 



