52 On Cystic Oxide, 
no opportunity of paying attention to any urinary concre- 
tions to which I could have access, I have, to this time, 
seen only one other specimen of the same substance. This 
last is in a collection of calculi belonging to Guy’s hos- 
pital, given by Mr. Lucas, surgeon to that institution, 
having been formed partly by his father, and partly by him- 
self, in the course of their practice; and according to the 
present arrangement, (which, it is to be hoped, will not be 
altered) the calculus to which [ allude may be found by re- 
ference to No. 46 of that collection. It was extracted by 
the usual operation, from a man of 36 years of age, of 
whom no record is preserved, except that his name was 
William Small. It weighed, when entire, 270 grains. 
In appearance, these calculi resemble more nearly the 
triple phosphate of magnesia, than any other calculus ; but 
they are more compact than that compound is usually found 
to be: not consisting of distinct laminz, but appearing as 
one mass confusedly crystallized throughout its substance, 
Hence, instead of having the opacity and whiteness observ- 
able in fusible calculi, which consist of a number of small 
crystals cemented together, these calculi have a yellowish 
semi-transparency ; and they have also a peculiar glistening 
lustre, like that of a body having a high refractive density. 
When this substance is submitted to destructive distilla- 
tion, it yields foetid carbonate of ammonia, partly fluid, and 
partly in‘a solid state, and a heavy foetid oil, such as usually 
proceeds from animal substances; and there remains a 
black spongy coal, much smaller in proportion than is 
found after the distillation of uric calculi. 
Under the blow-pipe it may be distinguished from uric 
acid by the smell, which at no period resembles that of 
prussic acid ; but in addition to the usual smell of burnt 
animal substances, there is a peculiar foetor, of which I 
cannot give a correct idea, as I know no smell which it can 
be said to resemble. 
This species of calculus is so readily acted upon by the 
generality of common chemical agents, that its character 
may perhaps be most distinctly marked, by an enumeration 
of those feeble powers that it can resist. 
It is not dissolved (excepting in very small proportion) 
by water, by alcohol, by acetic acid, by tartaric acid, by 
citric acid, or by saturated carbonate of ammonia. 
The solvents, on the contrary, are far more numerous, It 
js dissolved, in considerable quantity, by muriatic acid, by 
nitric acid, by sulphuric acid, by phosphoric acid, and by 
oxalic acid, 
It 
