42 Dr. Pearson's Experiments and Observations 
acid readily fuses, and, uniting to the phosphate of lime, com- 
poses superphosphate of lime, a very fusible substance. 
The phosphate of ammoniac being dissolved out by water, 
or caustic alkaline lye, the remaining matter is infusible, being 
phosphate of lime. 
A very hard, brittle, and blackish intestinal calculus of a 
dog, from Mr. Wilson, was found to be of greater specific 
gravity than human urinary calculi, and to have the same 
composition as that of the dog above described. 
This also was found to be the composition of a white, smooth, 
round, intestinal calculus of a horse, the specific gravity of 
which was 1,7 9 1 * 
The same composition was discovered, on examining a very 
hard, gray, brittle, laminated, quadrilateral concretion, said to 
be from the urinary bladder, but which, I think, was more pro- 
bably from the intestines, of a horse. 
II. On a Calculus from the urinary Bladder of a Rabbit. 
This is also a curiosity, being the only instance I have seen. 
I am likewise indebted to Mr. Thomas for this specimen, 
which he very kindly sent me, fitted up as a preparation, in- 
eluded in the bladder itself. Mr. Thomas found this concretion, 
on dissecting a perfectly healthy and very fat rabbit. 
This specimen is spherical, and of the size of a small nut- 
meg. It is of a dark brown colour, has a smooth surface, is 
hard, brittle, and heavy. When broken, it appeared to consist 
of concentric laminas. Its specific gravity was 2. 
i. Under the blowpipe it grew black, and emitted the smell 
of animal matter while burning ; at last it ceased to emit any 
