URINE. 345 



type and the octahedral type (Fig. 99, below). Either form may 

 occur in the sediment of neutral, alkaline or acid- urine, but both 

 forms are found most frequently in urine having an acid reaction. 

 Occasionally, in alkaline urine, the octahedral form is confounded 



FIG. 99. 



% 



'- ~ * 



CALCIUM OXALATE. (Ogden.) 



with " triple phosphate " crystals. They may be differentiated from 

 the phosphate crystals by the fact that they are insoluble in acetic 

 acid. 



The presence of calcium oxalate in the urine is not of itself a 

 sign of any abnormality, since it is a constituent of normal urine. 

 It is increased above the normal, however, in such pathological con- 

 ditions as diabetes mellitus, in organic diseases of the liver and in 

 various other conditions which are accompanied by a derangement 

 of digestion or of the oxidation mechanism, such as occurs in cer- 

 tain diseases of the heart and lungs. 



Calcium Carbonate. Calcium carbonate crystals form a typical 

 constituent of the urine of herbivorous animals. They occur less 

 frequently in human urine. The reaction of urine containing these 

 crystals is nearly always alkaline, although they may occur in am- 

 photeric or in slightly acid urine. It generally crystallizes in the 

 form of granules, spherules or dumb-bells (Fig. 100, p. 346). 

 The crystals of calcium carbonate may be differentiated from cal- 

 cium oxalate by the fact that they dissolve in acetic acid with the 

 evolution of carbon dioxide gas. 



Calcium Phosphate (Stellar Phosphate). Calcium phosphate 

 may occur in the urine in three forms, i. e., amorphous, granular or 

 crystalline. The crystals of calcium phosphate are ordinarily 

 pointed, wedge-shaped formations which may occur as individual 

 crystals or grouped together in more or less regularly formed 

 rosettes (Fig. 76, p. 224). Acid sodium urate crystals (Fig. 102, 



