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agents in causing the contraction of the heel; for, when the pressure is 
removed from their inner surfaces, they tend to assume their natural 
position, in virtue of their elasticity, and the pressure they exert upon the 
sénsitive frog, forces the heel into its original shape. 
’ 
CARTILAGINOUS APPARATUS OF THE HorsE’s Foor. 
A, external face of the lateral cartilage; B, superior border; C, posterior border ; 
D, anterior lateral ligament bordering the cartilage in front; E, flexor 
tendons; F, extensor tendons; G, coffin bone. 
4 
Briefly, then, they may be said to expand, when the foot is on the 
ground; ahd to assist contraction, when the weight which forces the 
sensitive frog upwards and outwards, is removed from the foot. Professor 
Williams, in short, holds that these lateral appendages act, as it were, 
“elastic sides,” preventing undue expansion of the soft parts of the 
coronet and heel. 
The term side-bone, we have said, denotes a bony or ossified 
condition of the lateral cartilages. This condition is commonly met with in 
heavy draught horses, and is but rarely seen in the lighter breeds. It is 
almost always met with in the fore feet, though in rare instances it has been 
observed on the hind ones. In the latter situation, it is never known to 
occasion lameness. The lateral cartilages are of lesser size here, and, being 
of less functional importance, are semseqmently much less liable to become 
diseased. 
We may now proceed in the first place to examine the causes of this 
very common form of disease among our heavy draught horses. Some 
“authorities compute that over fifty per cent. of the heavy draught horses 
become affected with this disease by the time they have attained the age of 
six or seven years; but, according to our own computation, sixty 
: per cent. is not an exaggerated estimate of this common form of morbid 
action, Why is this? Indubitably this morbid process depends, as do 
