397 
Gouty and Urinary Concretions. 
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 
flattened surfaces, so as at first sight to appear crystallized. 
These I find to be phosphorated lime in the state of neu- 
tralization, 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 
upon 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 acid of nitrated quicksilver, phosphoric acid is rea- 
dily 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 crystal- 
lization. 
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, although the quan- 
tities were very minute. The particles of sand which are so 
3 F 2 
