34S CALCULI. 



Experiments phoric acid was added to one ounce of distilled water. Of 



and observa- ^j^jg ^^rgak acid impregnation, one drop was sufficient to 



tions on urme, r o ? i 



fcc. turn the infusion of litmus of as clear a red as the mine- 



ral acids do; whilst seven of urine manifested but very 

 weak effects of acidity, and required some time to shew 

 •any. If the urine, therefore, does not exceed its natural 

 standard of acidity, we have nothing to apprehend. And 

 here, indeed, we must again admire the wonderful wisdom 

 of Providence. The occasion (may I be allowed to say so, 

 and that, too, before so competent an assembly ?) required 

 some chemical discrimination. It was necessary to care- 

 fully provide for the expulsion of the recrementitious part 

 of the osseous fabric (which is very considerable) out of the 

 system : but as this salt is insoluble in an aqueous vehicle, 

 such as the urine, nothing more would be necessary, to ob- 

 viate this difficulty, than a certain degree of super-satura- 

 tion, or state of acidule, which would more effectually pro- 

 vide for its solubility, and its elimination. But by going 

 thus far, whilst it attended to one excretion only, it would 

 have entirely forsaken its charge of another, committed also 

 to this fluid; and, by this degree of super-saturation, pre- 

 cipitate, retain in the system the uric acid, and occasion 

 as frequent an occurrence of gravelly and calculus com- 

 plaints, amongst mankind in general, as now occurs among 

 the gouty. It, therefore, prudently formed that degree only 

 of acidulous phosphat of lime, which, though insoluble out 

 of the body, was sufficiently soluble, when assisted by its 

 temperature. Nay, even for wise purposes, it has given a 

 degree of latitude to this temperature, which, though nar- 

 row and confined indeed, is sufficient for its purposes : but 

 where it precisely terminates I am not at present prepared 

 to say, though so easily determined. 



Let us now, for a moment, consider how far any morbid 

 deviation, from this healthy standard, (which sometimes 

 happens,) may throw light on this subject. The most con- 

 siderable, that I am acquainted with, occurs in the in- 



, stance of gouty urine, rendered towards the decline of 



the paroxism. A single drop of this, though in a turbi4 

 state, affects the vegetable blues, with an energy, equal, 

 or, perhaps, superior, to that of the strongest acetous acid; 



and 



