368 DISEASES OF THE HORSE’S FOOT 
If lameness is met with at all, then it is where we have 
a foot that is in other respects unsound, with badly con- 
tracted heels and upright ‘stumpy’ hoof, or where side- 
bones have occurred in a young animal, and have already 
reached a large size before the horse is put to labour. In 
this latter case, the added effects of concussion and the 
evil influences of shoeing are sufficient to turn the scale. 
Directly the animal, previously sound, is asked to work, 
lameness is the result. 
It follows, therefore, that side-bone in the feet of young 
animals is of far more serious import than when occurring 
in older horses. In a nag animal they constitute a positive 
unsoundness, and lameness in this case is more often than 
not an accompanying symptom. 
Causes. To commence with, we may remark that, 
although met with sometimes in very early life, side-bones 
are seldom, if ever, congenital, and that more often than 
not they may be looked for in animals of three years old, 
or older—seldom earlier. They appear, in fact, only when 
the animal is shod and commences work. 
This at once suggests two of the principal factors in their 
causation—namely, concussion and loss of normal function. 
Directly the horse is put to work he has for a great part of 
his time to travel upon roadways—either macadamized 
roads or town sets—where everything is calculated to bring 
concussion about. In addition to that he has the lateral 
cartilage itself thrown largely out of action by shoeing. 
We explained in Chapter III. (p. 66) that the chief function 
of the cartilage was to take concussion received by the 
plantar cushion and direct the greater part of it outwards 
and backwards. Now, with the animal shod, the plantar 
cushion does not itself, as normally it should, receive con- 
cussion. By the shoeing the frog is lifted from the ground, 
and the plantar cushion, together with the cartilage, taken 
largely out of active work. In other words, the normal 
outward and inward movements of the cartilage are enor- 
mously reduced. 
It is fair, we think, to take it that the mere fact of the 
