34 On Gravelly and Calculous Concretions. 



in a well closed phial, and laid on a sand heai which did not 

 exceed the temperature of 100 degrees. After being taken 

 out, and dried, the weight was found, as before, twenty-two 

 grains. 



From these experiments, then, we may conclude, that cal- 

 culi of the uric acid kind arc uisoluble in carbonated watery 

 and that Dr. Percival, whose cijara-Jter as a pliilosopher, as- 

 well as a physician, deservedtv stands so high, must have 

 operated upon concn-tions of a dift'eient kind ; more espe- 

 ciallv as in his experiments there was a loss of several grains- 

 in only a few ounces of mephiiic water, whilst none appeared 

 in ours, though in several pounds of that fluid. He must 

 have then operated upon some of a different and highly so- 

 luble kind. 



E.i'periinnit V. 



One -half of a calculus, of the ammoniacaf magnesiam 

 kind, \Acighing 100*5 grains, was suspended, as usual, for 

 ibrtv-eiiihi hours, in Noolh's apparatus : temperature 50 

 degrees. Upon being taken out, and dried, was found to^ 

 weigh JV2-H3 arains; so that its loss amounted to 7'S7, or 

 rather more than seven grains three quarters. And here we 

 have an explanation of the result of Dr. Percival's experi- 

 ments, by supposing that the calculi he employed must have 

 been of this species ; the e.xtven)e solubility of which, in so 

 weak and innocent a menstruum-, should excite the earnest 

 hope of our voung gentlemen, in the surgical dc[)artn)ent,. 

 of effecting its solution by injections of carbonated water 

 into the bladder. To su-ch safe trials thev must be encou- 

 raged bv the pleasing consideration that this kind forms a, 

 laree proportion of the human urinary calculi. On these 

 occasions the u aler should not be too highly impregnated, 

 lest the sudden expansion of the gas under the human tem- 

 nerature might excite the bladder to reject it loo quickly. 

 This inconvenience, however, must be in part obviated hy 

 the necessity of previou>lv warming the injection to about 

 ^he temperature of 80 degrees ; a precaution never to be 

 omitted. But to return to the alkaline earths and salts : — 

 Exjuiriment VI. 



©ne-half of a uric acid calculus was suspended, for forty- 

 eight 



