368 
A. LIAUTARD. 
centrated.”* We will later draw conclusions from this fact. 
It remains for us to examine how the os pedis transmits to the 
intermediate horny box, insensible between the ground and the 
living tissues, the pressure thrown upon its articular surface. 
Does the os pedis come down the horny box, or does it move 
backwards by its posterior border ? .Reasoning and observation 
of facts prove to us that it is immovable in the hoof. Let us try 
to show it: 
A. —If the os pedis was movable'and could come down in the 
hoof, it would compress the velvety tissue, and, as a consequence 
of its delicate texture, this would be crushed, and severe pain 
produced. It is true that in the posterior region of the foot the 
plantar cushion compresses the layer of that tissue underneath 
without injuring it. But the velvety structure of the anterior 
parts of the foot is interposed between two hard bodies, the upper 
one especially, while that of the posterior part is in connection 
superiorly with an organ, supple by excellence, the plantar cushion, 
at least in the physiological condition, and inferiorly in a great 
part of its extent with the deep layers of the frog, also very elastic. 
B. —If the os pedis was movable, the pedal apparatus would 
not have offered the rigidity neeessary to the impulsion, in an 
animal strong and rapid in its actions as the horse is. 
C. —If the sole had had for duty to be a means of support for 
the os pedis, this bone would come down in a marked manner in 
cases where the sole is entirely removed, as in some diseases, 
or after surgical operations. Nothing of this sort takes place. 
D. —The navicular bone is, we know, independent, at least 
in some measure, of the os pedis. This independence would have 
been unnecessary if the third phalanx could, like the navicular 
bone, be submitted to these motions of lowering and raising. 
E. —If this os pedis was moving backwards, the most favorable 
moment for this would be when all the sum of pressure is con¬ 
centrated upon it, that is when the other phalanges are straight¬ 
ened in their axis. But at this moment this becomes impossible 
because the tendon of the perforans muscle, being attached to the 
semi-lunar crest, lias a tendency to straighten this bone. 
* Merche—Priucipaux Systemes de Ferrure. 
