EFFECTS OP MAGNESIA ON URIC ACID. 
77 
diminished, and in three weeks every symptom of disease had 
disappeared. 
In February, 18 1 2 , having persevered in the use of mag- 
nesia, with little intermission, I was informed that the sand 
had returned, that increasing the quantity of magnesia had pro- 
duced no good effect, and that alkalies materially aggravated 
his complaint by disagreeing with the stomach, and greatly in- 
creasing the urinary deposit. 
On examining the sand, I found that, instead of consisting, Ma^uesia im- 
as formerly, of uric acid, it was composed of a mixture of the 
thf deposit 
ammoiiiaco-magnesian phosphate with phosphate of limej he does nut con- 
was directed to abstain from magnesia and alkalies, and to adopt ***[j°* 
a plan of treatment which it is the object of the second section 
of this paper more particularly to explain. 
The foregoing is a well-marked case of uric gravel with a 
I strong tendency to form calculi, materially relieved by the use 
of alkaline remedies : it illustrates their usual effects when 
. carelessly persevered in, and shews the advantage with which 
■magnesia may, in such instances, be employed : it also exhibits 
I the effect of magnesia and the alkalies, in producing the de- 
I posit of white sand (or phosphates) in the urine, when the 
fred sand (or uric acid) has been removed. 
The cases which follow are selected, from among others. 
I to explain the best mode of preventing the formation of white 
I sand, and to shew the most effectual treatment where it is a 
(natural deposit in the urine, or where it has been induced by 
(the incautious exhibition of alkaline medicines. 
Section II. 
The white sand so frequently voided by persons labouring Treatment 
tonder calculous complaints, was first analysed by Dr. Wol- 
^ ^ posit consists 
llaston*, who found it composed of ammoniaco-magnesian of am. mat;- 
[ phosphate, either alone or mixed with variable proper- 
ttiens of phosphate of lime. The use of acid medicines in 
• PhIL Trans, ir^. 
these 
