in the Structure of Calculi. 231 
monia, I am induced to believe that the evolution of ammonia 
depends in all instances upon the decomposition of the am- 
moniacal salts contained in the calculus, more especially of 
the ammoniaco-magnesian phosphate, and that no substance 
which can be called urate of ammonia , exists in calculi. 
The mulberry calculus (oxalate of lime) I have but rarely 
met with. In those preserved in the Hunterian Collection, 
there is a large relative proportion of phosphate of lime, and 
of uric acid. The purest of them afforded 
Oxalate of lime 
Grains. 
65. 
Uric acid 
16. 
Phosphate of lime 
15 * 
Loss in animal matter 
4 - 
100. 
When calculi of the urinary bladder increase to a very 
large size, they are generally composed of two or even three 
of the above mentioned varieties, the ammoniaco-magnesian 
phosphate being situated externally, and in the greatest abun- 
dance. 
The largest calculus which I have seen, weighed, when re- 
cently removed from the bladder, twenty-three ounces and 
twenty-six grains. It consisted of a large mulberry or oxa- 
late of lime calculus, the nucleus of which was uric acid, sur- 
rounded by a considerable quantity of the ammoniaco-mag- 
nesian phosphate in a very pure state. 
Another very large calculus, weighing fifteen ounces and 
a half, consisted of a nucleus of uric acid, enveloped in the 
ammoniaco-magnesian phosphate, not however pure, but in- 
tersected by several laminae of uric acid. 
