168 HE HORSE. 
attention should be paid rather to improve the general health than to 
subdue the local affection. 
SMALL TUMOURS, of about the size of a pea, often form upon the. tendons, 
especially the “back sinews” of the fore legs) They may or may not 
occasion lameness, but they are always to be regarded with suspicion. As 
long as they remain indolent, they are better left alone ; but when they 
produce inflammation and pain, the best remedy is the biniodide of 
inercury ointment, described at page 456. 
DISEASES OF CARTILAGE AND SYNOVIAL MEMBRANE. 
CaRTILAGE is subject chiefly to ulceration. When this occurs, its cells 
become enlarged and crowded with corpuscles, which burst and discharge 
their contents ; the intercellular structure at the same time splits into 
bands, which, together with the corpuscles, form a fibro-nucleated mem- 
brane on the face of the cartilage. In old horses, the ulcerated cartilage 
covering the tibial surface of the astragalus is sometimes converted into a 
soft fibrous substance, avhich ultimately assumes the appearance of hard 
and dense bone, commonly known as “ porcellaneous or ivory deposit.” 
It is accompanied by no symptoms of inflammation ; the sole evidence of 
disease, during life, being a stiffness of the joint, and a peculiar grating or 
crackling noise during all attempts at movement. When caries of “the 
head of a bone has caused a loss of substance, the cartilage dies, and is 
gradually broken down by decomposition ; but this cannot be said to be 
a disease of the cartilage itself’ With the exception of navicular disease 
(which will be included under the diseases of the foot), ulceration of 
cartilage is not very common in the horse. 
ACUTE INFLAMMATION OF THE SYNOVIAL MEMBRANE is seldom met w ith ; 
but a chronic state, inducing an excessive secretion of synovia, is extremely 
common. The most usual situation is at the hock, where the swelling 
has received the name of bag-spavin and thoroughpin ; but they also 
occur at the fetlock and knee joints ; in the former case being sometimes 
confounded with windgalls, which are inflamed burse mucose. (See 
Windgalls.) 
Boc-sPavin is very apt to attack young horses, when they are over- 
worked, before being fully seasoned ; but it may occur at all ages. It 
shows itself at the inner side of the joint, because here the ligaments are 
wider apart, and there is more room fof distension. Its seat is the capsule 
between the tibia and astragalus, which is here unprotected by any strong 
fibrous covering, and readily yields to the gradual pressure of the secretion 
from its internal surface. (See fig. 22, G H, page 362.) 
THOROUGHPIN may be either an increased secretion of the synovial 
capsule, between the astragalus and os calcis, or between the scaphoid 
and cuneiform bones, or of the bursa mucosa lying between the tendo 
Achillis and the tendo perforatus. In the first of these cases,’it often 
coexists with bog-spavin, and the synovia may be made to fluctuate from 
one bag to the other, the only line of demarcation being the astragalo- 
calcanean ligament. (See fig. 22, G, page 362.) 
Both bog-spavin and thoroughpin may exist, or either separately, without 
oceasioning lameness ; but where they are just established, there is gene- 
rally some small degree of active inflammation, which causes a slight 
lameness on first going out of the stable, but soon disappearing. 
The treatment should be by pressure, kept up for a long time, by means 
of a carefully-adjusted,tvuss, alternated with cold affusion, and the use 
