910 



THE SENSORY APPARATUSES. 



Fig. 492. 



sends to this ligament, and to the tendon of the anterior extensor of the 

 phalanges, a fibrous expansion that becomes fused with that of the opposite 

 side. 



The fibro-cartilages comprise in their structure a mixture of fibrous and 

 cartilaginous tissue, though the mixture of these is far from being perfectly 

 homogeneous, or everywhere in the same proportions. 



The cartilages of the fore feet are thicker and more extensive than those of 

 the hind ones. 



(The lateral fibro-cartilages are peculiar to Solipeds.) 



2. Plantar Cushion. — The plantar cushion is a kind of wedge, situated 

 in the space between the two cartilaginous plates of the third phalanx, and 

 between the perforans tendon and the lower part of the hoof. Its shape allows 

 it to be considered as having an antero-superior and 

 an infero-posferior face, a base, summit, and two lateiril 

 borders. 



The antero-superior face is moulded on the aponeu- 

 rotic 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 per- 

 forans tendon " (Bouley). This expansion is prolonged, 

 above, to the fetlock, where it is confounded with the 

 superficial fascia of the metacarpal region ; it is mar- 

 gined, 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 attached within the 

 retrossal process. 



The infero-fosterior face of the cushion is covered 

 by the keratogenous membrane, and presents at its 

 middle the pyramidal body, a prominence exactly like 

 that of the frog, to which it corresponds. It shows, 

 then, in front, a single conical prolongation, and be- 

 hind, 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 expansion, which separates it from the skin of the 

 pastern ; 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 into the plantar face of the pedal bone, in front of the semi- 



LOWER FACE OF THE HORSE'S 

 FOOT, THE HOOF HAVING 

 BEEN REMOVED. 



1, Heel; 2, coronary cushion; 

 3, branch of the plantar 

 cushion; 4, median lacuna, 

 or commissure; 5, lamina; 

 of the bars ; 6, velvety 

 tissue of the sole. 



