802 



THE AFPABATUS OF THE SENSES. 



Fig. 372. 



allows it to be considered as having an aniero-superior and an infero-posterior 

 face, a lase, summit, and two lateral borders. 



The antero-swperior face is moulded oq the aponeurotic expansion of the 

 perforans tendon, and is "covered by a cellulo-fibrous membrane, the proper 

 tunic of the plantar cushion, which is continuous, on its inner face, with the 

 fibrous septa by which this organ is traversed, and adheres by its external 

 or anterior face to the reinforcing sheath interposed between it and the 

 perforans tendon."— Bouley. This expansion is prolonged, above, to the 

 fetlock, where it is confounded with the superficial fascia of the meta- 

 carpal region ; it is margined, laterally, by two 

 small, very strong ligamentous bands which, at 

 their middle portion, cross, in a very oblique 

 manner, the fasciculus formed by the vessels and 

 nerves of the digit. Each of these bands is fixed, 

 superiorly, to the base of the rudimentary digit 

 known as the ergot, and to the knob of the lateral 

 metacarpal bone; their inferior extremity is at- 

 tached within the retrossal process. 



The infero-posterior face of the cushion is 

 covered by the keratogenous membrane, and pre- 

 sents at its middle the pyramidal body, a promi- 

 nence exactly like that of the frog, to which it 

 corresponds. It shows, then, in front, a single 

 conical prolongation, and behind, two divergent 

 prominences separated by a median excavation. 



The base of the apparatus lies behind, and is 

 inclined upwards; it is divided by a depression 

 into two lateral masses — the bulbs of the plantar - 

 cushion — on the inside of which the posterior 

 prominences of the pyramidal body reach, and 

 which become confounded, outwardly, with the 

 posterior and inferior angle of the cartilaginous 

 plates. This portion of the cushion is, like the 

 anterior face, covered by a cellulo-fibrous expan- 

 sion, which separates it from the skin of the pas- 

 tern ; this expansion is attached, by its lateral 

 margins, to the posterior border of the cartilages, 

 and continued, superiorly, on the surface of the 

 anterior expansion, with which it soon unites. 



The summit (point or apex) forms a sharp border, more or less regularly 

 convex ; it is fixed iuto the plantar face of the pedal bone, in front of the 

 semilunar ridge and the insertion of the perforabs tendon, with which the 

 plantar cushion mixes its fibres at this part. 



The lateral borders are wider behind than before, in consequence of the 

 wedge-like shape of the whole organ ; they are continuous with the inner 

 face of the lateral cartilages, as already indicated in describing the latter. 



The organisation of the plantar cushion differs much from that of the 

 cartilages. It has for its base a fibrous structure, continuous with that which 

 constitutes the fandamental framework of these ; this structure is very cl6se 

 towards the infero-posterior part of the organ, and becomes gradually looser 

 as it leaves this region ; the meshes it contains are filled with a yellow pulp 

 composed of fine, elastic, and connective fibres, in the midst of which some 

 adipose cells are found. (I have attentively examined this yellow pulp, and 



LOWER FACE OP THE HORSE S 

 FOOT, THE HOOF BEING RE- 

 MOVED. 



1, Heel ; 2, Coronary cushion ; 

 3, Branch of the plantar 

 cushion ; 4, Median lacuna ; 

 5, Lamina of the hars; 6 

 Velvety tissue of the sole. 



