Prof. E. D. Smith on Calculous Affections. 303 
Admitting, however, that satisfaction has been obtained 
with regard | to the peculiar nature of the disease, a question 
of much importance still remains to be discusse 
In the case of a tendency to form uric calculi, which are 
supposed to be the most common, it is not a matter of in- 
differenee what particular alkali is used to counteract this 
tendency. “Mr. Brande clearly shows that an alkali, ad- 
ministered to a calculous patient, stands no chance of reach- 
ing the uric concretion in a caustic state; for the ure con- 
tains both phosphoric and carbonic acid tincombined: jut 
experiment clearly shows that neither carbonates nor sub- 
carbonates exert any ‘sensible action on uric acid: in other 
words the affinity of the uric acid for alkalies is weaker than 
the affinity of carbonic acid for the same bodies: therefore. 
alkaline liquors cannot act as solvents of the uric caleuli.”* 
eriments made upon healthy urine, tend to show that 
the internal use of sub-carbonates of pot-ash and soda oc- 
casions a considerable and speedy deposition of the phos- 
phates (a circumstance, that ought to excite a caution in the 
fashionable use of soda-water, by persons in health) proba- 
bly by neutralizing the free acids, which hold these ate in 
solution 5 while the similar use of the alkaline earth, _ nae 
r oe tee : ct but in a ite 
gree. Baie 1e infere: been drawn, that in calcu- 
lous eases, which need arson feniailes magnesia is to be 
preferred; and the particular mode of its action has been 
accounted: for, both by the assumption that the disposition 
to generate uric acid in undue quantity commences in the 
stemach, and by the fact, that magnesia from its insoluble 
nature, will remain in the stomach ‘jong enough to combine 
with any acid that may be formed there—if this acid does 
not exist in the stomach, the use of the sub-carbonates 0 
potash and soda does little good ; because, from their ae 
solubility, they are ca arried too rapid! y out of the seat of 
disease and being conveyed into the bladder, may pro- 
duce it mary there by causing a deposition, which would not 
otherwise have taken place, while magnesia, retarded by its 
sasolabiiee ates efficaciously upon n the acid and is totally 
neutralized by it. In case of no acid existing, then both 
the sub-carbonated alkalies and magnesia will be ecnei 
* Edinburgh Review? ‘November 1820. 
