URINE. 365 



blood coagulation within the urinary tract. They frequently occur 

 as nuclei of other forms of calculus. They are rarely found. 



Cholesterol Calculi. An extremely rare form of calculus some- 

 what resembling the cystine type. 



Indigo Calculi. Indigo calculi are extremely rare, only two 

 cases having been reported. One of these indigo calculi is on ex- 

 hibition in the museum of Jefferson Medical College of Philadel- 

 phia. 



The scheme, proposed by Heller and given on page 364, will be 

 found of much assistance in the chemical examination of urinary 

 calculi. 



