ANATOMY OF THE FOOT. 581 



The homy substance which constitutes the hoof has a fibrous 

 aspect ; it is hollowed aU over by cylindrical canals, whose superior 

 extremities, widened into a funnel shape, cover the papiUse of the 

 matrix of the hoof, either at the coronary band or velvety tissue, 

 while the inferior open ia the wall upon the plantar border, in the 

 sole and frog, at the external or inferior face. These canals are 

 rectilinear, except those of the frog, which are flexuous ; their 

 diameter varies from 0, 02 to 0, 2 or Od""-"- These tubes are not 

 only hollowed in the horny substance ; they have also proper walls, 

 of very great thickness, formed of numerous concentrical layers, 

 received into each other. These are lamellse of pavimentous 

 epithelium, which constitute the horny tissue ; in the walls of the 

 homy tubes, they are grouped flatwise around their inferior canals, 

 and stratified from withiu outward, so as to form successive and 

 concentrical layers; iu the intertubular horn, these lamellse are 

 not stratified in a direction parallel to that of the tubes, but at 

 right angles with it. Around the tubes, the lameUse have an 

 oblique intermediate direction. A granular opaque substance fills 

 up the space lying between the horny tubes and the papiUse. 



The hoof, which is a part of the epidermis, develops similarly, 

 that is, by the constant formation of ceUs in the layer which cor- 

 responds to the mucous malpighian body, at the expense of the 

 plasma thrown off by the numerous blood-vessels of the keratoge- 

 nous membrane. The velvety tissue is the starting point of the 

 elements of the sole and frog ; the periopUo band is the organ 

 secreting the periople ; and the coronary band proper, the matrix 

 of the wall. Upon these different parts, the epithehal cells multi- 

 ply and flatten into lamella, in the direction of the surface of the 

 keratogenous membrane, as they spread from it. The wall then 

 grows from its superior to the inferior border, and the other parts 

 of the wall from their internal to their external face. The viUosi- 

 ties of the coronaiy band and of the velvety tissue are the organs 

 around which accumulate the epithelial cells; their presence 

 defines, consequently, the tubular structure of the horn. 



The laminse, in the physiological state, do not co-operate in a 

 sensible manner with the formation of the waU ; the keraphyUous 

 laminse form themselves at the coronary band, at the origin of the 

 podophyUous; they descend with the waU, gUding at the surface 

 of the layer of ceUs which separates them from the laminated 

 tissue, a movement of descent which is facilitated, however, by the 



