ANATOMY AND PHYSIOLOGY OP THE HORSe’s FOOT. 393 
structure of the fibre, the nature of its hitherto undefined 
contents, and the disposition of the cells on each side of the 
fibre. A preparation of this kind is copied in the annexed 
drawing (fig. 16). From this it will be seen that each horn- 
tube or fibre bears a great resemblance (microscopically) to a 
human hair, in consisting of a cortical or outer investing 
series of layers of cells of a dense texture (apparently), laid 
Fig. 16. — Side view of horn-fibre from the wall of the hoof ; after heating 
in caustic potash. Magnified 500 diameters, a. Interfibrous cells. 
b . Cortical or wall cells of the fibre, c. Medullary or internal cells of 
the fibre. 
upon one another in the direction of the fibre, and a softer 
looking, or medullary , series filling tbe interior. 
The cortical cells, which form the chief portion of every 
fibre, when viewed in this manner, appear to be longitudi- 
nally striated and fasciculoid, and when treated with acids or 
alkalies, it is seen that they are elongated, flattened, dense- 
looking, and rigid. It is to their lamellar disposition that 
the tube owes its fibrous aspect. The outer layers gradually 
incline from the vertical to the horizontal position, before 
finally amalgamating with the interfibrous cells. 
The medullary cells which fill the tube, and appear to the 
naked eye in a transverse section of the wall or sole fibres as 
minute white circular points, are generally small, and in 
shape round or polyhedral. They have no very definite 
arrangement, not being subjected to any appreciable degree 
of pressure, though careful observation may discover that 
they are laid to some extent in superposed rows which give 
rise to a cordon that follows the axis of the fibre. Near the 
