VOL. LXXXVII.] PHILOSOPHICAL TRANSACTIONS. 21 (J 



acid; and being now freed from redundant lime, will, on evaporation of the marine 

 acid, assume a crystalline form. As the laminated calculus contains no excess of 

 lime, that will at once yield such crystals: their appearance will be described in 

 the succeeding experiment. 



Calculus from the prostate gland. — There is still another calculus of the urinary 

 passages, though not of the bladder itself, which deserves notice, not from the 

 frequency of its occurrence, but from having been supposed to give rise to stone 

 in the bladder. I mean the small stones which are occasionally found in the pros- 

 tate gland. Those that I have seen, and which, by favour of Mr. Abernethy, I 

 have had an opportunity of examining, were from the size of the smallest pin's 

 head to that of pearl barley, in colour and transparency like amber, and appeared 

 originally to have been spherical ; but from contiguity with others, some had flat- 

 tened surfaces, so as at first sight to appear crystallized. These I find to be phos- 

 phorated lime in the state of neutralization, tinged with the secretion of the 

 prostate gland. 



(18) A small fragment being put into a drop of marine acid, on a piece of glass 

 over a candle, was soon dissolved; and on evaporation of the acid, crystallized in 

 needles, making angles of about 6o° and 120° with each other. Water dropped 

 on the crystals would dissolve no part of them; but in marine acid they would re- 

 dissolve, and might be re-crystallized. — (19) Vitriolic acid forms selenite with the 

 calcareous earth. — (20) By aid of nitrated quicksilver, phosphoric acid is readily 

 obtained. 



(21) When heated this calculus decrepitates strongly ; it next emits the usual 

 smell of burnt animal substances, and is charred, but will not become white 

 though partially fused. It still is soluble in marine acid, and will in that state 

 crystallize more perfectly than before. Hence I conclude, that these stones are 

 tinged with the liquor of the prostate gland, which in their original state (18) 

 somewhat impedes the crystallization. This crystallization from marine acid is so 

 delicate a test of the neutral phosphorated lime, that I have been enabled by that 

 means to detect the formation of it, though the quantities were very minute. The 

 particles of sand which are so generally to be felt in the pineal gland, have 

 this for their basis; for I find that after calcination they crystallize perfectly from 

 marine acid. I have likewise met with the same compound in a very pure state, 

 and soft, contained in a cyst under the pleura costalis. 



On the contrary, ossifications, properly so called, of arteries and of the valves 

 of the heart, are similar to earth of bones, in containing the redundant calcareous 

 earth ; and I believe also those of veins, of the bronchiae, and of the tendinous 

 portion of the diaphragm, have the same excess; but my experiments on these 

 were made too long since for me to speak with certainty. To these I may also add 

 the incrustation frequently formed on the teeth, which, in the only 2 specimens 

 that I have examined, proved to be a similar compound, with a very small excess 

 of lime. 



p p 2 



