VOL. LXXXVIII.] PHILOSOPHICAL TRANSACTIONS. 267 



that of human urinary concretions, in general ; which I have learned by experi- 

 ments is also the case with urinary and intestinal concretions of other brute ani- 

 mals, especially with those of the horse. The specific gravity of the present 

 calculus was 1.7. That of one from the urinary bladder of the human subject, 

 of the sort called mulberry calculus, and which consisted almost entirely of uric 

 oxide, was \.60Q. That of another human urinary concretion, of the same com- 

 position as the former, but quite smooth, extracted by Mr. Ford, was 1.571. 



1. The present calculus of the dog had no taste, nor smell, till exposed to fire. 

 2. Under the blow-pipe it first became black, and emitted the smell of common 

 animal matter; it next smelt strongly of empyreumatic liquor cornu cervi, and, 

 after burning some time, became inodorous, and white, and readily melted, like 

 super-phosphate of lime. 3. On trituration with lye of caustic soda, there was a 

 copious discharge of ammonia. 4. It dissolved on boiling in nitric acid: the 

 solution was clear and colourless ; and, on evaporation to dryness, left a residue of 

 white bitter matter, which, under the blow-pipe, emitted weakly the smell of 

 animal matter. 5. On distilling a mixture of I50grs. of this concretion pul- 

 verized and 2-i- pints of pure water, to 3 oz., the distilled liquid was found to con- 

 tain nothing but a little ammonia. The 3 oz. of residuary liquid, being filtrated 

 and evaporated, yielded 20 grs. of phosphate of ammonia, with a little animal 

 matter; and the residuary undissolved matter amounted to 67 grs. 6. These 67 

 grs., being triturated with 4 oz. of caustic soda lye, discharged very little ammo- 

 nia. On distilling this mixture to 1 oz., a very small proportion only of ammo- 

 nia was found in the distilled liquid. The residuary oz. of alkaline liquid was 

 filtrated, and mixed with the water of elutriation of the undissolved matter. One 

 half of those liquids, on evaporation to dryness, afforded a dark brown matter, 

 amounting to 20 grs., which consisted of phosphate of lime and animal matter. 

 To the other half of the alkaline liquids was gradually added muriatic acid, which 

 occasioned a deposit, in small proportion, of matter that dissolved in nitric acid, 

 but which, on evaporation to dryness, left behind only a brownish matter, consist- 

 ing of phosphate of lime and animal matter. 7- The residuary insoluble sub- 

 stance in caustic lye, (6), under the blow-pipe, first turned black, and then white, 

 but could not be melted. By diluted sulphuric acid it was decompounded. On 

 the addition of nitrate of mercury, to the filtrated liquid, it yielded phosphate of 

 mercury; and with oxalic acid, it afforded oxalate of lime; but no sulphate of 

 magnesia was found remaining after these precipitations were produced. These 

 experiments fully demonstrate, that the above concretion of a dog contained none; 

 of the uric or lithic oxide above described, but that it consisted, principally at least, of 

 phosphate of lime, phosphate of ammonia, and animal matter. The present instance 

 leads me to explain the reason of the fusibility of calculi. This is demonstrated, by the 

 above experiments, to depend on the discharge and decomposition of the ammonia 

 of the phosphate of ammonia, during the burning away of the animal matter; 

 hence the residuary phosphoric acid readily fuses, and, uniting to the phosphate of 



m m 2 



