in the Structure of Calculi. 233 
having been removed by an operation soon after it had passed 
into the bladder. It appeared to consist chiefly of phosphate 
of lime. 
The incrustation upon the hazel nut was also destitute of 
uric acid. 
SECTION IV. 
Of Calculi of the Urethra. 
All those that were examined had escaped from the bladder 
while very small, and had afterwards lodged in the membra- 
nous part of the urethra, where they had increased in size, and 
formed a cavity in which they were more or less embedded. 
Two of these calculi were broken. 
The fragments consisted in one instance, of ammoniaco- 
magnesian phosphate, and phosphate of lime, with a small 
portion of uric acid : and in the other the fragments were 
composed entirely of the ammoniaco-magnesian phosphate. 
The third calculus was of a very remarkable appearance ; 
its form being that of a perfect sphere, about half an inch in 
diameter. It was coated with small but very regular crystals 
of the triple phosphate in its purest state. On account of the 
singularity of the form and external appearance of this cal- 
culus, it was not sawn through ; the nucleus, in all proba- 
bility, is a small kidney calculus, which lodging in the urethra 
has become coated with triple phosphate. 
SECTION V. 
Analysis of Calculi from other Animals . 
1. The Horse. 
A. From the kidney . 
MDCCCVIII H h 
