HEREDITARY DISEASES OF HORSES. 
585 
and synovial connections of the bones of the hock, and 
usually of those between the cuneiform medium and meta- 
tarsal bone. Effusion occurs, forming an exostosis or bony 
tumour on the antero-internal part of the hock, attended 
during its formation with great pain and consequent lame- 
ness. Violent and continued exertion, especially when the 
animal is growing, is the usual immediate cause of this 
disease. The amount of strain of the parts affected, and the 
consequent liability to the disease, are always greatest where 
the width and strength of the limb below the hock are dispro- 
portioned to its width and strength above the hock. Horses 
of such conformation are unusually predisposed to the most 
troublesome and serious cases of spavin, and hand down to 
their progeny a similar conformation and predisposition. 
Other bony deposits besides spavins are also more apt to 
affect some families than others. This tendency may depend 
on an endeavour on the part of nature to strengthen a local 
weakness, as well as on a general disposition to the formation 
of exostosis — a disposition always more frequent and stronger 
in the horse than in most other animals. 
Curl is a strain of the calcaneo-cuboid, or posterior straight 
ligament of the hock, causing pain and swelling on the pos- 
tero-internal part of the joint. Horses most subject to it are 
those in which the hock is straight and the os oalcis short 
and inclining forwards. 
Of all the complaints to which horses are liable there is 
none more frequent, more troublesome, or more tedious, than 
strain of the back tendons . It usually consists in rupture of 
the minute fibres of the tendo perforans, or of the strong 
check ligament attached to it. To repair this injury inflam- 
mation is established ; effusion soon follows, and occasionally 
thickening and shortening of the limb. The frequency and 
severity of this accident might be greatly diminished by 
breeding only from animals with sound well-formed limbs. 
The chances of its occurrence are least in horses having well- 
shaped knees, sufficiently large both in their anterior and 
lateral aspects, with the tendons prominent from the fetlock 
upwards — a formation which gives a flat appearance to the 
limb when viewed from the side. Horses, on the other hand, 
with round legs and small knees, to which the tendons are 
tightly bound down, are especially subject to strains, on 
account of the want of that full prominence of the posterior 
part of the knee which is found in limbs of a more perfect 
conformation, and which gives a mechanical advantage to the 
tendons passing over it. With the aid of this lever the 
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