REVIEW. 
79 
villo-papillary apparatus just described as project into them. I 
have described these last organs as being from -g^ths to -^ths of 
an inch in length. Now, the canals just mentioned hold the 
same length (which consequently becomes buried up to their 
point of junction in the substance of the sole and crust) of living 
parts, of a most delicate organization, destined to secrete, to 
produce, to nourish, and to regenerate the hoof. It is these 
villo-papillary prolongations which on occasions are heated, 
altered and burnt within the horny substance in the course of 
the process of hot-shoeing, as I shall point out further on. 
I will now, still keeping the object of inquiry in view, sav a 
few words on the structure of those portions of the crust and 
sole which are heated by the shoe. 
Up to this day it has been believed that the horn of the crust 
was composed of fibres agglutinated together by horny matter ; 
and that the substance of the sole was constituted of super- 
imposed layers of horn, exfoliating by degrees in scales. This is 
true. But if we would prosecute the inquiry further than with 
our eyes — if, for example, we dissect the horn after having 
caused it to undergo certain preparation, and we examine it 
through lenses of different powers, we distinctly perceive that 
the horn of the crust, the sole, and, I may add, the frog and 
periople, is veritably composed of filaments in fibres represented 
by the agglutinated hairs; but that these fibres are hollow, con- 
stituting so many tubes in distinct canals, into every one of 
which dips one of the villo-papillae we have been speaking of ; 
and these are the canals which, cut across when the sole is 
being pared out and the crust cut down, constitute the pores or 
porosities of the hoof. 
These canals, which contain neither greasy matter similar to 
what enters into the hair, nor marrow analogous to what is 
found in birds’ feathers, though still an organic substance, are not 
of the same diameter throughout their extent ; their caliber 
being much more considerable, and their transverse section 
exhibiting porosities so much larger, in proportion as the divi- 
sion is made nearer to the parts containing the villo-papillse 
ensheathed within them. 
Lastly, these canals, as I have fully assured myself, are 
themselves constituted of delicate epithelial layers, elongate or 
oval, bearing a bulb more or less distinct, whose keratine or 
horny matter constitutes its primordial element. These epithe- 
liums are attached to prolongations of organic substance, lining 
the canals, and serving as supports to them. 
The lamella? of the canals of the crust are placed longitudi- 
nally one upon the other, like the tiles upon a roof, while in the 
sole they are placed horizontally, and lie flatwise upon one 
