£38 On the Differences in the Structure of Calculi. 



stances which attend the formation of th<.- second species of 

 calculus sediment or deposition in the urine, are~considered. 



The ammoniaco-magnesian phosphate appears under two 

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

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

 sand, and is frequently mixed with variable porportions of 

 phosphate of lime. In the latter it makes Us appearance after 

 the urine has remained undisturbed for some hours in an 

 open vessel, generally in the form of a fine pelhcie, or of 

 crystalline laminae, which when collected and dried bear 

 some resemblance to boracic acid. 



Its putting on tbi? form is accounted for* from its being 

 held in solution in the first instance bv 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 phosphoric 

 acid present, which keeps another portion of the ammoniaco- 

 magnesian phosphate, and also some lime (in the state of 

 super-phosphate of lime) in solution. 



It is therefore obvious, that whenever the urine is deprived 

 of a portion of the acid which is natural to it, the deposition 

 of the triple phosphate, and phosphate of lime, more readily 

 takes place : this is effected by the exhibition of the aikalis. 

 It mav therefore be asserted, that although alkaline medi- 

 cines often tend to diminish the quantity of uric acid, and 

 thus to prevent the addition of that substance in its pure 

 state, to a calculus in the bladder j they favour the deposi- 

 tion of the phosphates. 



It cannot be doubted that the alkalis reach thebladder,since 

 in cases where large doses of sub-carbonate of potash have 

 been exhibited, I have seen evident traces of it in the urine. 

 Where the phosphates only are voided, it has been pro- 

 posed to dissolve the calculus by the exhibition of acids, and 

 more especially the muriatic acid. 



Dunne the use of the muriatic acid, the phosphates are 

 either diminished or disappear altogether; and even some- 

 times the urine acquires an additional acidity : a solution of 

 that part of the calculus which consists of the phosphates 



miaht 



