GRAVEL. 459 



[Calculi in which oxalate of lime predominates have been 

 analysed by Scharling : 



1. 2. 



Oxalate of lime . . 37 63-5 



Phosphate of lime . . 6-2 



Ammoniaco-magnesian phosphate . 39 



Water . . .10 



Organic matters . .13 



i 30-3 



See also analysis 161, and the above analysis of Laugier.] 

 Cystic calculi have been analysed by Taylor and Bley : 



Taylor. Bley. 



Cystin .... 10-0 6-2 



Aramoniaco-magnesian phosphate . 10-0 36'6 75-0 



Phosphate of lime . . 38-0 7'0 



Carbonate of magnesia . . 57'1 



Uric acid . . . 18-0 



Animal matter and loss . . 42-0 



Both the calculi analysed by Bley were taken from the 

 bladder of the same man; the first weighed 1'75, and the 

 second 2 grains. 



URINARY GRAVEL. 



Gravel has naturally the same composition as calculi; uric 

 acid is, however, the most frequent constituent. In form, 

 gravel is round or angular, not unfrequently crystalline; its 

 colour is most commonly red, but sometimes pale yellow, gray, 

 or brown. The rules already given for the analysis of calculi 

 apply equally to gravel. After having ascertained by the blow- 

 pipe whether the gravel is perfectly destroyed by heat, or 

 whether it leaves an ash that burns white, we then proceed in 

 accordance with the directions given in p. 431. Uric-acid gravel 

 is frequently crystalline, and red or purple, but occasionally 

 of a bright yellow colour, or white. The urine from which it 

 separates is concentrated, highly coloured, and has usually a 

 strong acid reaction. 



White gravel is usually composed of phosphate of lime with 

 ammoniaco-magnesian phosphate, and occasionally of oxalate 

 of lime. The ammoniaco-magnesian phosphate crystallizes in 

 beautifully regular prisms, (often of considerable size,) as de- 



