23B Mr. W. Brande on the Differences 
We are entirely ignorant of the cause of the formation 
of the oxalate of lime, or mulberry calculus. I have fre- 
quently looked for oxalate of lime in the urine of calculous 
patients, but have never been able to detect it, and as it does 
not exist in healthy urine, it must be regarded as a morbid 
secretion. Its mode of formation seems to resemble that of 
uric acid, since small kidney calculi, composed of oxalate of 
lime, have in a few instances been voided ; and in these cases, 
as far as my own enquiries go, the persons have been much 
less liable to a return of the complaint, than where uric calculi 
have been voided. 
In some rare instances we meet with calculi of the bladder 
which are destitute of uric acid, and of oxalate of lime, the 
nucleus being composed of a little loosely agglutinated am- 
moniaco-magnesian phosphate, and the whole calculus con- 
sisting of that substance, with variable portions of phosphate of 
lime : in two cases I have met with calculi of this kind, com- 
posed of the triple phosphate only : they seem to be entirely 
formed in the bladder. 
Having taken this short view of the formation of calculi, I 
shall now enquire into the action of solvents, employed either 
with a view of effecting their solution, or of preventing their 
formation and increase. 
Solvents are of two kinds. 
1. Alkaline. 2. Acid. 
In the exhibition of these, the practitioner is usually guided 
by the chemical composition of the calculous matter voided 
by urine. 
The different kinds of gravel voided by persons labouring 
under calculous complaints, may be classed in two divisions. 
