URINARY APPARATUS. 



193 



recognized by the fact that the addition of acetic acid causes 

 an evolution of gas. 



b. Oxalate of lime crystallizes in square octahedra that 

 have strong light-refracting power, other forms occur but 

 are not characteristic. Acetic acid does not affect oxalate 

 of lime, hydrochloric acid dissolves it. It occurs in small 

 quantities in alkaline urine, to a greater extent in acid urine, 

 but is of no importance for diagnostic purposes. 



c. Uric acid and its salts are normal constituents of 

 the urine of carnivora but traces of them also occur in the 

 urine of herbivora. 



They commonly occur as an amorphous powder or in 

 the form of crystals ; whetstone, rhombic plates, pointed crys- 



Fig. 46. 



Hippuric Acid. 



Triplephosphate Crystals. 



tals, frequently occurring in the form of minute druses. A 

 characteristic consists in the peculiarity that, on crystallizing, 

 they attract the pigment of the urine which gives them a 

 yellowish brown color. They dissolve in a solution of caus- 

 tic potash, and they are precipitated in the form of rhombic 

 prisms by {he addition of hydrochloric acid. 



d. Hippuric acid and its salts form rhombic quadrilat- 

 eral prisms and needles which dissolve in hydrochloric acid. 

 Normal constituent of urine of horses. 



