428 PHYSIOLOGICAL CHEMISTRY. 



specially characteristic of the alkaline fermentation. The urine in 

 alkaline fermentation becomes paler and is often covered with a 

 fine membrane which contains amorphous calcium phosphate and 

 glistening crystals of triple phosphate and numerous micro-organ- 

 isms. 



Non-organized Sediments. 



Uric Acid. This acid occurs in acid urines as colored crystals 

 which are identified partly by their form and partly by their prop- 

 erty of giving the murexid test. On warming the urine they are 

 not dissolved. On the addition of caustic alkali to the sediment 

 the crystals dissolve, and when a drop of this solution is placed on a 

 microscope-slide and treated with a drop of hydrochloric acid, small 

 crystals of uric acid are obtained which are easily seen under the 

 microscope. 



Acid Urates. These only occur in the sediment of acid or 

 neutral urines. They are amorphous, clay-yellow, brick-red, rose- 

 colored, or brownish red. They differ from other sediments in 

 that they dissolve on warming the urine. They give the murexid 

 test, and small microscopic crystals of uric acid separate on the 

 addition of hydrochloric acid. Crystalline alkali urates occur very 

 rarely in the urine, and as a rule only in such as have become 

 neutral but not alkaline by the alkaline fermentation. The crys- 

 tals are somewhat similar to those of neutral calcium phosphate, 

 but are not dissolved by acetic acid but give a cloudiness therewith 

 due to small crystals of uric acid. 



Ammonium urate may indeed occur as a sediment in a neutral 

 urine which at first was strongly acid and has become neutralized 

 by the alkaline fermentation, but it is only characteristic of am- 

 moniacal urines. This sediment consists of yellow or brownish, 

 rounded globules which are often covered with thorny-shaped 

 prisms and, because of this, are rather large and resemble the thorn- 

 apple. It gives the murexid test. It is dissolved by alkalies with 

 the development of ammonia, and crystals of uric acid separate on 

 the addition of hydrochloric acid to this solution. 



Calcium oxalate occurs in the sediment generally as small, 

 shining, strongly-refractive-quadratic octahedra, which on micro- 

 scopical examination remind one of a letter-envelope. The crys- 



