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XIV. Experiments on Human Calculi . In a Letter from Mr. 
Timothy Lane, F. R. S. to William Pitcairn, M. D 
F. R. S. 
Read May 5, 1791. 
SIR, 
I T will give me much fatisfaftion fhould the following ex- 
periments, made twenty years ago, fo far meet your ap- 
probation, as to be thought worthy the notice of the Royal 
Society. 
The Lixivium Saponarium of the late Pharmacopoeia, pre- 
pared with the addition of fo much lime as nearly to free the 
fait of tartar of its fixed air *, having been ufed as a medicine 
for the ftone and gravel fome years before, and its effe&s 
found very unequal, I thought it neceffary to examine dif- 
ferent calculi, then collefted, both as to the effedl of the above 
lixivium, and of fire, upon them. 
Great difparity was obferved ; fome being diffolved, and 
others fcarcely altered in their figure. 
When tried by fire, fome were nearly evaporated by a red 
heat, and others retained their form. 
Different parts even of the fame calculus, varied confi- 
derably. 
* See Letter to Dr, Hsseroen, Medical Tranfa&ions, Vol, I. p. 112. 
4 That 
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