On a Cyst upon the Olfactory Nerve of a Horse. 27 
was greatly interfered with, and probably rendered very 
obtuse. But of this, as well as the existence or otherwise of 
pain from the pressure of the cyst, we are without means of 
ascertaining. 
On placing the specimen under the microscope, and viewing • 
it with a two-inch object-glass, I was surprised to find a large 
octohedral crystal of oxalate of lime, with beautifully de- 
fined facets freely floating in a limpid fluid which distended 
the walls of the cell. There appeared to be no obstacle to the 
passage of the crystal from side to side of the cavity or in any 
other direction when the specimen was placed in different posi- 
tions, its weight quickly carrying it to the most depending part. 
The walls of the cell have every indication of being composed 
of layers of areolar tissue spread out in a membranous form ; 
they are not, however, of uniform thickness throughout, 
although everywhere very translucent. Towards the circum- 
ference or periphery of the cell on one side there exists 
a bell-shaped spot (a Fig. 1, PI. IV.), which is thinly co- 
vered with membrane, but surrounded with many fibres, far 
more dense than in any other part. Beside the crystal within 
the interior there is a small mass of granular-like matter, 
which can also be made to vary its position ; this mass is 
marked b. 
The occurrence of this deposition of the oxalate of lime in 
this situation is the more interesting from the circumstance 
that this salt of lime is very rarely met with in the urine of the 
horse, in which the carbonates, on the contrary, are very com- 
mon. Various forms of the carbonate of lime are noticed in 
the urine of the herbivora, produced by causes disturbing its 
ordinary mode of crystallization ; but none of these forms can 
be confounded with the octohedral arrangement of the oxalate. 
The priority of the formation of the cell or the crystal is not 
easy to be determined, it being possible that the blood of the 
animal, from impregnation with the oxalate of lime, deposited 
this salt in the place it was found, and that subsequently a 
cell enclosed it to prevent any serious ill consequences to the 
surrounding organism; or it may be that the cell was first 
formed, and then the salt was effused into its interior, where 
it led to the e^^udation also of fluid. It is perhaps right to 
mention, in conclusion, that several capillary vessels are to be 
observed ramifying upon the walls of the cyst, and that it was 
firmly held in its place by fibres of areolar tissue. I may also 
add that the crystal has not been measured to ascertain its 
exact size, but that it can very readily be seen by unassisted 
vision. 
