304 On Gravelly and Calculous Concretions. 



this property ; so very feeble, indeed, that A will often not 

 atl'ect ail infusion of red cabbage, whilst it turns with lit- 

 mus, and sometimes, but feeblv, with this most delicate of 

 all acid tests. A single drop of phosphoric acid was added 

 to one ounce of distilled water. Of this weak acid impreg- 

 nation one drop was sufficient to turn the infusion of litmus 

 of as clear a red as the nnneral acids do ; whilst seven of 

 urine manifested but very weak effects of acidity, and re- 

 quired some time to show any. If the urine, therefore, 

 does not exceed its natural standard of acidity, we have no- 

 thing to apprehend. And here, indeed, we must again ad- 

 mire the wonderful wisdom of Providence. The occasion 

 (may I be allowed to say so, and that, too, before so com- 

 petent an assembly?) required some chemical discrimina- 

 tion. It was necessary to carefully provide for the expul- 

 sion 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 obviate this difficulty than a 

 certain degree of super-saturation, or state of acidule, which 

 would more effectually provide for its solubihty and its eli- 

 mination. 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, precipitate, retain in the system the 

 uric acid, and occasion as frequent an occurrence of gra- 

 velly and calculous complaints, amongst mankind in gene- 

 ral, as now occurs among the gouty. It therefore prudently 

 formed that degree only of acidulous phospiiate 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 tem- 

 perature, which, though narrow and confined indeed, is 

 sufficient lor its purposes; but where it precisely terminates 

 1 am not at present prepared to say, though so easily dc- 

 tc) ijiined. 



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 instance 

 of gouty urine rendered towards the decline of the parox- 

 ysm. A single drop of this, though in a turbid state, af- 

 fects the vegetable blues with an energy equal, or perhaps 

 superior, to that of the strongest acetous acid ; and requires 

 a very considerable increased proportion of lime water to 

 decompose it, for obvious reasons. This we find always 



depositing, 



