HEREDITARY DISEASES OF HOUSES AND CATTLE. 159 
leaving too much for the other parts of the joint to perform, 
and concussion is the common consequence, followed by in- 
flammation and lameness, sometimes connected with curbs , at 
other times spavins or thorough-pins ; and it is not an uncom- 
mon case to see all three of these diseases in the hock at one 
time. There are other formed hocks, which are even more 
disposed to curbs than the one just mentioned; such are the 
“ sickle-hock 55 or “ cow-hock.” 
We can scarcely name any disease of the horse which 
affords stronger evidence of a hereditary tendency derived 
from peculiarity of structure than the one we have been con- 
sidering. We have also some interesting examples of disease 
in the feet arising from faulty and peculiar conformation. 
(<?.) Diseases of the Feet . — Most persons acquainted with the 
feet of horses will recognize their strong tendency to disease, 
arising from faulty formation. Sometimes the hoofs are dis- 
proportionate to the frame— they may be too small, without 
sufficient base to support the superincumbent weight — ren- 
dering the footing insecure, or too large and unweildy, ren- 
dering the action slow and awkward. At other times the 
crust of the hoof is naturally weak, arising from a faulty 
secretion of horn. Such hoofs are generally uneven, indented, 
and wrinkled, and have invariably flattened soles, with a dis- 
position to become pumiced. Again, we occasionally find the 
crust morbidly dry and brittle, arising from the absence of 
that peculiar tough and elastic horny material which consoli- 
dates and binds, in perfectly formed hoofs, the longitudinal 
fibres of the crust together. Feet of this character are par- 
ticularly disposed to sand-craclcs . All these defects we have 
been describing in horses 5 feet are found to exist not only in 
different but in the same breed, and are most certainly pro- 
pagated in breeding. 
The Navicular Disease is another striking example of here- 
ditary disease, to which horses are liable, arising from pecu- 
liarity of structure. Those most disposed to it have slender 
bodies, low action, strong upright hoofs, narrow heels, and 
great concavity of soles. Lameness is soon produced in 
horses of this description, when the hereditary tendency 
exists, from exciting agents of various kinds, such as expo- 
sure to heated, fermented litter, imperfect shoeing, fast road- 
work : whilst animals free from this hereditary proclivity are 
capable of withstanding all these influences. 
The contraction usually seen in diseased feet of this kind 
is perhaps more commonly the consequence than the cause 
of the lameness ; but sometimes it may act as a predisposing 
agent — the former in cases when inflammation precedes the 
