36 DISEASES OF THE HORSE'S FOOT 



os pedis and the plantar cushion. To the irregularities of 

 the latter body — its bulbs, pyramidal body, and its lacunae 

 — It is closely adapted. Its surface may, therefore, be 

 divided into (a) The Sensitive Frog, and (b) The Sensitive 

 Sole. 



(a)The Sensitive Frog is that part of the velvety tissue 

 moulded on the lower surface of the plantar cushion. The 

 shape of the plantar cushion has already been described as 

 identical with that of the horny frog. It only remains to 

 state that, like the coronary cushion, the surface of the 

 sensitive frog is closely studded with papillae. The cells 

 clothing the papillae are instrumental in forming the horny 

 frog. 



(b) The Sensitive Sole. — As its name indicates, this is 

 the portion of the keratogenous membrane that covers the 

 plantar surface of the os pedis. It also is clothed with 

 papillae, which again give rise to the formation of that part 

 of the horny box to which they are adapted — namely, the 

 sole. 



3. The Podophyllous Tissue, or Sensitive Laminje. — 

 This portion of the keratogenous membrane is spread over 

 the anterior face and sides of the os pedis, limited above by 

 the coronary cushion, and below by the inferior edge of 

 the bone. It presents the appearance of fine longitudinal 

 streaks, which, when closely examined with a needle, are 

 found to consist of numerous fine leaves. These extend 

 downwards from the lower border of the coronary cushion 

 to the inferior margin of the os pedis. At this point each 

 terminates in several large villous prolongations, which 

 extend into the horny tubes at the circumference of the 

 sole. At the point of the toe this membrane sometime, 

 shows a V~ s h a P e d depression, into which fits a y^-shaped 

 prominence on the inner surface of the wall at this point. 



The sensitive laminae increase in width from above to 

 below. Their free margin is finely denticulated, while 

 their sides are traversed from top to bottom by several 

 folds (about sixty), which, examined microscopically, are 

 seen to consist of secondary leaves, or laminellce. 



