ON THE STRUCTURE OP CALCULI. 4# 



carbonic acid gas is given off: and also, when lime water is 

 poured into urine, a precipitate appears, consisting of phos- 

 phate and carbonate of lime. 



Lime water, on account of the insoluble compound which JjJJJJJjJJJ 

 lime forms with carbonic and phosphoric acids, is even more tionable. 

 objectionable as a solvent, than the alkalis. 



It may however be said, that, if these means prevent the Howfarpalli- 

 increase of a calculus, material relief is afforded to the pati- atlVe ' 

 ent. How far the exhibition of alkaline remedies can be 

 recommended upon these grounds will appear, when the cir* 

 cumstances, which attend the formation of the second spe- 

 cies of calculous sediment or deposition in the urine, are 

 considered. 



The ammoniaco-magnesian phosphate appears Under two Ammoniac^ 

 forms : it is either voided in a solid state, or in solution. In SJJttl 

 the former case it bears a good deal of resemblance to a 

 white sand, and is frequently mixed with variable proportions 

 of phosphate of lime. In the latter it makes its appearance 

 after the urine has remained undisturbed for some hours in 

 an open vessel, generally in the form of a fine pellicle, or of 

 crystalline laminae, which when collected and dried bear 

 some resemblance to boracic acid. 



Its putting on this form is accounted for, from its being 

 held in solution in the first instance by carbonic acid, and as 

 this flies off, the triple salt makes its appearance. If a por- 

 tion of the urine be preserved in a phial closely stopped, the 

 carbonic acid cannot escape, and consequently no phosphate 

 is observed to separate. There is also a quantity of phos- 

 phoric acid present, which keeps another portion of the am- 

 moniaco-magnesian phosphate, and also some lime (in the 

 state of superphosphate of lime) in solution. 



It is therefore obvious, that, whenever the urine is de- Injurious «f- 

 prived of a portion of the acid which is natural to it, the ecW ° *' 

 deposition of the triple phosphate, and phosphate of lime, 

 more readily takes place : this is effected by the exhibition 

 of the alkalis. 



It may therefore be asserted, that, altjhougb alkaline me- 

 dicines often tend to diminish the quantity of the uric acid r 

 fnd thus to prevent the addition of that substance in its pure 



Vol. XXII.— Jan. 1809. £ state 



