LAMENESS IN HORSES. 
485 
in the absence of shoes, by degrees repaired, not only their 
lost width, but their sound and prominent frogs as well, time 
being given them for such changes to be brought about. The 
action of the frog is but a secondary power in the expansion of 
the hoof, and when the heels of the hoof are fixed, as they are by 
those of the shoe, has but feeble power, unaided by the great ex- 
pansive effect of the wall of the hoof, of itself to dilate the heels. 
Want of Weight of Body and Force of Action in 
the subject may account for lack of expansive power, and 
so for the predominance of the contractile force. Light horses 
having slender bodies and going near the ground, with hoofs 
of a strong and upright and growing fibre, are very sub- 
ject to contraction from the diminished power there exists in 
them to expand a foot requiring greater force of expansion ; 
though, if they should happen to possess high stamping action, 
this power is much augmented during the time they are going. 
But, even in this case, were it not for the unceasing counter-active 
effect of the shoe — or, in other words, were the foot set at liberty 
by being unshod — it would be only under certain circumstances 
that the operations of nature would be overcome by any such 
deficiency. Indeed, when horses are shod with tips, so long as 
the heels are left at liberty, it rarely — never , I believe I may 
say — happens that this cause, or even want of pressure to the 
frog, operates to the production of contraction. Standing tied 
up in the stable no doubt tends to favour the operation of such 
causes; but even then, were they not aided by the imprison- 
ment of the hoof by the shoe, their influence would be com- 
paratively feeble. 
The direct Causes of Contraction are neither numerous 
nor potent when put into competition with those we have 
mentioned — the indirect : at the same time, when operant with 
the latter causes or such as tend to prevent expansion, they be- 
come to a certain degree influential. No agent can be said to 
be direct save one whose effect is to produce actual contraction. 
Such influences as operate in occasioning shrinking of the dead 
hoof or shrivelling of dead horn, such as droughts or heat or 
evaporation, may be expected to take more or less effect upon 
the living hoof, if not in their ordinary form, at least when ap- 
plied in any inordinate degree. Heat has this tendency ; and 
so has long-continued drought, or any tiling that robs the hoof 
of its moisture. The heat of the stable; standing upon wet or 
fermenting litter, or the absence of moisture to the hoof in a 
situation and at a time when its own natural juiciness or hu- 
midity is departing from it, may, any one or all such like in- 
fluences, take such effect as to dispose (he hoof to contraction. 
Still, such agents will be greatly more effectual on shod than on 
unshod hoofs. 
