in the Structure of Calculi . 227 
SECTION III. 
Of Calculi of the urinary Bladder. 
Calculi met with in the bladder are of four kinds. 
1. Those formed upon nuclei of uric acid, from the kidney. 
2. Those formed upon nuclei of oxalate of lime, from the 
kidney. 
3. Those formed upon sapd or animal mucus, deposited in 
the bladder. 
4. Those formed upon extraneous bodies introduced into 
the bladder. 
They were arranged under the following divisions. 
1. Calculi, which from their external appearance, consist 
chiefly of uric acid. 
These calculi vary in colour from a deep reddish brown, 
to a pale yellowish brown. 
They are either entirely soluble in a solution of pure 
potash, or nearly so. 
During their solution they frequently emit the odour of 
ammonia. 
When acetic acid is added to their alcaline solution, a pre- 
cipitate possessing the properties of uric acid is obtained. 
2. Calculi, composed chiefly of the ammoniaco-magnesian 
phosphate, or of phosphate of lime, or of mixtures of the two. 
These calculi are externally of a whiter appearance than 
the former. 
Some perfectly white, others gray, occasionally exhibiting 
small prismatic crystals upon their surface ; others again soft 
and friable, a good deal resembling chalk. They are further 
characterised by their solubility in dilute muriatic acid. 
Gg2 
