CYSTIC CALCULUS IN THE HORSE. 
125 
at length to a chronic form of inflammation, which results in 
the secretion of a large quantity of mucus of a more viscid 
character than natural, and this continuing to act as a 
ferment, induces the like changes in the urinary secretion, so 
that the deposition of carbonate of lime oftentimes becomes 
excessive. Sometimes this is retained in the bladder in the 
form of a loosely aggregated mass, there being a specimen in 
the College Museum in which the urinary cyst is filled to 
distension with it. It weighs thirteen pounds avoirdupois. 
At other times, by the exertion of the force of corpuscular 
attraction, the particles aggregate together, and thus a true 
calculus is formed. 
The absence of the phosphates in these concretions has 
been noticed by some writers. It is, according to Liebig, 
owing to the small amount of phosphorus, or of the phos- 
phates existing in the food of the graminivora. He more- 
over says, that “ the organism collects all the phosphates 
produced by the metamorphosis of the tissues, and employs 
them for the development of the bones and the phosphorized 
constituents of the brain. The organs of excretion do not 
separate these salts from the blood. The phosphoric acid 
which, by the change of matter, is separated in the uncom- 
bined state, is not expelled from the body as phosphate of 
soda, but we find it in the solid excrements in the form of 
insoluble phosphates. 55 
Occasionally crystals of oxalate of lime are found asso- 
ciated with these concretions taken from the horse. Espe- 
cially is this the case in those specimens forwarded from 
India. Will our friends inform us if calculous affections 
are common in that country, and what are the probable causes 
which give rise to them ? - 
At one time the origin of this compound was assigned to 
some of the varieties of the rumex, probably the Bumex 
Acetosa , which is so abundantly met with among the grasses, 
and which, being dried with them in the making of hay, the 
animal partook of the same as food, and thus conveyed the 
salt into the blood, whence it was eliminated by the kidneys. 
A more probable view, however, of its formation is, that a 
mal-assimilation of the ingesta takes place from an impair- 
ment of the digestive function, and a change analogous to 
that which obtains in the formation of carbonate of ammonia 
results ; for, if two equivalents of carbonic acid lose one of 
oxygen, oxalic acid is formed. 
2 Ea. Carbonic Acid C 2 0 4 — 0 = C 2 0 3 Oxalic Acid, 1 Eq. 
This acid, from its superior affinity for lime, will imme 
