646 ANATOMY AND PHYSIOLOGY OF THE HORSE^S FOOT. 
direction and relative disposition of the fibres would be 
materially altered ; these, however, as we have seen, pass in 
exactly the same line and maintain the same distance from 
each other from top to bottom. The microscope does not 
reveal any accretion on the inner aspect of the wall. 
Neither does the microscope or polarized light attest that 
there is any distinction between the mass of the wall and the 
leaves on its inner face ; but that, on the contrary, they are 
merely continuations of that mass, and pass from between 
the inner strata of fibres ; that they are constituted, in fact, 
by the interfibrous cells arranged in a particular manner, and 
projected beyond the level of the wall, and that this arrange- 
ment can be traced for some distance into its substance. 
There is not the faintest indication that these keraphyllae 
have been added to it after it has left the generating surface 
of the coronary cushion and the commencement of the 
vascular laminae. 
The question then arises as to how the keraphyllae are 
formed, and what parts are chiefly concerned in their forma- 
tion. I think there can be no doubt whatever as to their 
being generated at the lower margin of the coronary cushion, 
at the part we have designated the coronary or white zone, and 
at the junction of this with the vascular laminae. We have 
remarked that in this situation the villi are so disposed as to 
leave narrow spaces between them, and that these spaces 
correspond to the more or less regular linear imprints in the 
cutigeral cavity which are continuous with the horny 
laminae ; this feature alone would almost suffice to prove 
that these leaves commence to be formed at the coronary 
zone, and that they are part and parcel of the wall itself, — 
not a subsequent formation proceeding from the podophyllae 
and merely attached to it by simple agglutination, as has 
been imagined. The horn-cells or epidermic material 
intended for the constitution of the laminae is formed on the 
surface of the coronary zone and between the vascular 
laminae at their origin, the latter serving as a mould, so to 
speak, in which this horn material receives its characteristic 
foliate shape. 
As a proof that under ordinary physiological conditions 
the vascular leaves do not secrete the horny ones, we may 
point to the fact that soon after their commencement there is 
no material difference in the width or thickness of the latter 
until their termination. This would not be the case did the 
podophyllae continue to throw out additional material 
throughout their length, for the constant accretion would 
notably affect the dimensions of the horn-leaves from above 
