THE APPENDAGES OF THE SKIN. 913 



separated from the podophyllous tissue by the plantar border of the foot, some- 

 what encroached upon posteriorly by the laminae corresponding to the bars, and 

 is continuous, above these laminaB, with the plantar cushion. 



The surface of the velvety tissue is studded with villi similar to those of the 

 coronary cushion, and about the same size. The longest are towards the cir- 

 cumference of this surface, and the shortest in the median lacuna of the pyra- 

 midal body ; all are lodged in the porosities on the inner surface of the horny 

 sole and frog. 



This tissue shows the same organization as the coronary cushion. The 

 vascular corium, forming its base, is thickened at its peripheral portion by a 

 fibrous network named the plantar reticulum, in the meshes of which are sustained 

 the veins of the inferior surface of the foot. 



3. Laminal Tissue. — This part of the keratogenous membrane is also 

 very frequently designated the podophyllous tissue (and still more frequently, in 

 this country, as merely the lamiyim). It is spread over tlie anterior face of the 

 third phalanx, occupying the interval between the plantar border of that bone 

 and the lower margin of the coronary cushion ; its width is, therefore, greater 

 at the anterior portion of the phalanx than on its sides, where the extremities of 

 the membrane are reflected below the bulbs of the plantar cushion on to the 

 velvety tissue. 



This membrane owes its name to the leaves it exhibits on its superficies ; 

 these are from five to six hundred in number — we have counted 560 — run 

 parallel to each other, and are separated by deep channels, into which are dove- 

 tailed analogous leaves from the inner side of the wall of the hoof ; they extend 

 from the white zone that hmits the inferior border of the coronary cushion — 

 where they are not so salient — to the plantar border of the foot, where they 

 each terminate in five or six very large villous prolongations, which are lodged 

 in the horny tubes at the circumference of the sole. 



The leaves {lamina) of the podophyllous tissue increase in width from above 

 to below ; their free margin is finely denticulated, and, under the influence of 

 any inflammatory cause (laminitis, ablation of the horny wall), these denticulse 

 become largely developed, and transformed into veritable papifla^. Their sides are 

 traversed by folds, about sixty in number, which pass uninterruptedly from top 

 to bottom. These secondary leaves, or lamellae, are fixed obliquely on the sides 

 of the lamiufe, as the barbules of a feather are attached to the barbs (Figs. 494, 

 4 ; 496, f," c!') 



The podophyllous tissue is not in immediate contact with the keraphyllous 

 tissue, or horny laminge ; between the two there is a mass of soft, elHptical cells, 

 always destitute of pigment, easily stained with carmine, and appearing to stud 

 the ramifications of the vascular laminse (Fig. 494, 4). A transverse section of 

 the union of the hoof with these laminae, when treated with carmine, presents a 

 very fine aspect, appearing as so many fern or acacia-of-Judsa leaves placed 

 between the keraphyllous laminae — the principal nerves and the secondary 

 nervules of the leaves, being represented by the lamina and its lateral ridges, the 

 limb of the leaves by the young cells spread around the latter. 



The structure of the podophyllous membrane resembles that of the other parts 

 of the keratogenous apparatus. Its corium is, like that of the peripheral portion 

 of the velvety tissue, separated from the os pedis by a fibrous reticulum, which 

 supports the veins, and forms, to some extent, the periosteum of the third 

 phalanx. 



