THE FOOT. 325 



The remarkably solid union between the hoof and the sensitive 

 tissues is due, above all, to the intimate dovetailing of the sensitive 

 laminae with the horny laminae. 1 



These two sets of laminae, however, are not simply placed in juxta- 

 position in a parallel manner,' but they interdigitate with one another 

 by the numerous secondary prolongations which they offer on their 

 lateral faces and which are disposed after the manner of the barbs of a 

 feather upon its stalk. This construction admits of a very slight 

 gliding of the keraphyllous laminae of the wall upon those, soft and 

 flexible, of the podophyllous tissue, whence, in consequence, the first 

 decomposition of force at their level. 



Besides, the wedge formed by the third phalanx not only descends 

 parallel to the wall, but describes a sort of vertical rotation, from the 

 pressure transmitted by the second phalanx to the navicular bone. 

 This pressure is first exercised upon the plantar aponeurosis, e, which 

 maintains the articular angle, and, secondly, upon the elastic plantar 

 cushion situated immediately below. Following this, there exist also 

 at this place two new structures whose elasticity, now called into 

 activity at the moment of the contact, notably diminishes the intensity 

 of the reactions. 



But the phenomena do not cease here. The plantar cushion, 

 strongly compressed from above to below by the weight of the body, 

 tends to depress the plantar arch at the same time that it elongates 

 transversely, where it is maintained by the two lateral cartilages. The 

 latter, flat, wide, supple, and very elastic, overlap behind the superior 

 border of the wall and sensibly separate from each other under the 

 influence of the eccentric pressure which they receive from the plantar 

 cushion. They are therefore opposed, in their turn, to the rotation of 

 the third phalanx in the interior of the hoof. 



Thus, little by little, the internal parts of the foot decompose the 

 reactions of the weight, by changing their form and relative situation, 

 and, finally, by concentrating their action upon the diverse parts of the 

 hoof, especially the frog, the quarters, and the sole. 



The sole is flattened and becomes less concave inferiorly ; its 



1 M. Fader has recently called attention to the remarkable manner in which the horny case 

 is attached to the living parts. According to him, in a horse of medium form, the laminae of the 

 foot being supposed to have an area of a square decimetre, the total surface of the principal and 

 secondary laminae, which he has had the patience to compute, should attain about one square 

 metre ! It can then be readily understood how this system of dovetailing of the laminae is cal- 

 culated to insure the intimate union of the horn and the flesh, to decompose the concussion, at 

 times enormous, which the ungual extremity receives, and to distribute uniformly the pressure 

 upon the whole of the internal face of the wall. 



(See, for more details, Bulletin de la Soc. cent, de med. vet<r., annee 1888, p. 494.) 



