on the Effects of Magnesia. 351 
been induced by the incautious exhibition of alkaline me- 
dicines. 
Section II. 
The white sand so frequently voided by persons labouring 
under calculous complaints was first analysed by Dr. Woi- 
Jaston *, who found it composed of ammoniaco-magnesian 
phosphate, either alone or mixed with variable proportions 
of phosphate of lime. The use of acid medicines in these 
cases was also first suggested by the same able chemist ; but 
although his valuable observations have been before the 
public for nearly fifteen years, I am not aware that any ex- 
periments have been made to ascertain what acids are best 
calculated to produce the desired effect, or to illustrate their 
mode of action. 
Since my former communication, I have lost no oppor- 
tunity of attending to this important subject, and hope that 
the conclusions, suggested by the following cases, will be 
deemed ‘satisfactory, and that their application in practice 
may lead to useful results. 
Case \. A gentleman, fifty years of age, who about ten 
years before had undergone the operation for the stone}, 
was attacked on the 14th of January 1810 with violent pain 
in the right kidney and ureter, which lasted two days; on 
the 17th, these symptoms subsided, and were followed by 
those of stone in the bladder, which continued for some 
days ; and although he had taken abundance of barley water 
and similar diluents, the stone showed no disposition to 
pass. On account of his former sufferings, this circum- 
stance rendered him extremely uneasy, and on the evening 
of the 21st he suffered several severe paroxysms of pain on 
attempting to make water. Under these circumstances, he 
was desired to take a purge, composed of two ounces of 
infusion of senna, two drachms of tincture of senna, and 
twenty grains of powdered jalapf. In three hours this 
began to take powerful effect, and during the violence of 
the operation, he was so fortunate as to void the calculus 
with his urine; it weighed eight grains. On the 28th he 
again suffered pain in the region of the kidneys, and voided 
* Philosophical Transactions 1797. 
+ ‘The stone extracted consisted of a nucleus of uric acid about the size of 
a pea, incrusted with a mixture of the phosphates. It was broken during 
the operation, but appeared to have been of the size of a pigeon’s egg. 
} I recommended this treatment in consequence of having heard Sir 
Everard Home state a case, in his Surgical Lectures, of a gentleman who 
suffered a bougie to pass so far into the urethra, that it could not be ree 
moved by any instrument, During the operation of a purge it was expelled 
with considerable force. 
much 
