470 REVIEW-BRIDGEWATER TREATISES, No. 4. 
have a foot in which strength and elasticity are combined. The 
elasticity is essentially necessary to prevent percussion in striking 
the ground ; and it is attained here through the oblique position 
of the bones of the leg and foot, the yielding nature of the 
suspending ligament, and the expansibility of the crust or hoof. 
So much depends on the position of the pastern bones and coffin 
bones, that, judging by the length of these and their obliquity, 
it is possible to say whether a horse goes easily without mounting 
it. When the hoof is raised, it is smaller in its diameter, and 
the sole is concave ; but when it bears on the ground it expands; 
the sole descends so as to become flatter; and this expansion of 
the hoof laterally is necessary to the play of the whole structure 
of the foot. Hence it happens, that, if a shoe be nailed in such 
a manner as to prevent the hoof expanding, the whole interior 
contrivance for mobility and elasticity is lost. The foot in trot¬ 
ting comes down solid—it consequently suffers percussion; and 
from the injury it becomes inflamed and hot: from this inflamma¬ 
tion is generated a variety of diseases, which at length destroy 
all the beautiful provisions of the horse^s foot for free and elastic 
motion. ‘"This subject,’^ says Sir Charles, “is of such general 
interest, that I may venture on a little more detail. The elastic 
or suspending ligament, spoken of above, passes down from the 
back of the cannon bone along all the bones to the lowest, the 
coffin bone; it yields, and allows these bones to bend. Behind 
the ligament the great tendons run; and the most prolonged of 
these, that of the perforans muscle, is principally inserted into 
the coffin bone, having at the same time other attachments. 
Under the bones and tendon, at the sole of the foot, there is a 
soft elastic cushion: this cushion is the fatty frog, and rests on 
the proper horny frog, that prominence of a triangular shape 
which is seen in the hollow of the sole. The soft elastic matter 
being pressed down, shifts a little backwards, so that it expands 
the heels, at the same time that it bears on the horny frog, and 
presses out the lateral part of the crust. We perceive that there 
is a necessity for the bottom of the hoof being hollow or con¬ 
cave ; first, to prevent the delicate apparatus of the foot from 
being bruised; and secondly, that elasticity may be obtained by 
its descent. We see that the expansion of the hoof, or properly 
the crust, and the descent of the sole, are necessary to the play 
of the internal apparatus of the foot. The crust is not equally 
elastic: the anterior part having to resist the whole strength of 
the animal, as in straining to drag a load, is very firm and ine¬ 
lastic, whilst the lateral parts and the heels expand under the 
pressure of the frog. 
“ That there is a relation between the internal structure and the 
