TUE APFESDAGES OF TEE SKIN. 



909 



Of the arteries, at pp. 636, 654 ; 

 Of the veins, at pp. 698 to 703. 

 Of the nerves, at pp. 865, 881. 



It remains to notice the complemmtary apparatus of the third phalanx, and 

 the keratot/e/ioii.s membrane. 



Prepiirtition. — The diBetctiou of tlie fibro-oartilafrt b \a made at the same time as that of the 

 articulation of tlie foot. A jjood idea of the shape of the plantar cushion can be obtained in a 

 longitudinal and median section of the digital region (Fig. 493), and on the piece prepared to 

 show the snbi'orneal tissue. This is obtained by two procedures. In the first, we wait until 

 decomposition has softeneil the cells lietween the hoof and the keratogeuous membrane, when 

 the hoof can be easily pulled off. In the second, the foot is kejit for several hours in boiling 

 water, then lield in a vice by the pastern while the tissues around the coronet are slij;htly cut 

 through ; a pair of shoeinir pincers is now employed at the heels in pulling the h(jof up and 

 down until it comes off. The foot is then washed to free it from the debris. (Tiie hoof can 

 also be reniuvcd by prolonged maceration, or by masting on a fire, wiieu it may be cut and torn 

 off by the farrier's knife and pincers). 



Ficr. 491. 



A. Complementary Apparatus of the Pedal Bone. — In the indication 

 we jjave of t!iis apparatus at p. 117, it was mentioned that it was composed of 

 two lateral pieces — the fibro-rfirtilar/es of the pedal 

 bone, united behind and below by the plantar 

 cushion — a fibrous, elastic mass, on which the 

 navicular bone rests, through the medium of the 

 perforans tendon. We will take this distinction 

 as the basis of oar study. 



1. Fibro-cartilages of the Pedal Bone. 

 — Each of these pieces represents a plate flattened 

 on both sides, having the form of an oblique- 

 angled parallelogram, and prolonged behind the 

 third phalanx. The external fare is convex, and 

 pierced with openings for the passage of veins ; 

 it slightly overhangs that of the pedal bone. The 

 internal face is concave, channeled by vascular 

 furrows, and covers, in front, the pedal articula- 

 tion, and the synovial cul-de-sac that projects 

 between the two lateral hgaments of that joint ; 

 below and behind, it is united to the plantar 

 cushion, either through continuity of tissue, as 

 at the inferior border, or by fibrous bands passing 

 from one to the other. The upper border, some- 

 times convex, sometimes rectilinear, is thin and 

 bevelled like a shell ; it is separated from the 

 posterior margin by an obtuse angle, in front of 



which this border is often broken by a deepnot<;h that gives passage to the vessels 

 and nerves of the digital portion. The inferior border is attached, in front, to 

 the basilar and retrossal processes ; behind the latter, it is reflected inwards to 

 become continuous with the tissue on tlie lower face of the plantar cushion. 

 The posterior border is oblique from before to behind, and above to below, and 

 joins the preceding two. The anterior border is oblique in the same direction, 

 and is united so intimately to the anterior lateral ligament of the pedal articula- 

 tion, that it cannot be separated from it except by an artifice of dissection It 

 60 



(hirizontal section of the 

 horse's foot. 



1, Front, or toe of the hoof; 2, thick- 

 Dess of the wall ; 3, laminae ; 4, 

 insertion of the extensor pedis ; 5, 

 OS pedis ; 6, navicular bone ; 7, 

 wings of the os pedis; 8, lateral 

 cartilage: 9, fle.\or pedis tendon; 

 10, plantar cushion ; 11, inflection 

 of the wall, or "bar;" 12, homy 

 frog. 



