390 ANATOMY AND PHYSIOLOGY OF THE HORSE ? S FOOT. 
the canals are contracted, and are filled with a white material, 
which some writers have designated cretaceous, others homo- 
geneous ; while the concentric laminae are proportionately- 
increased in number and compactness. 
The minute structure of the horn fibres has been examined 
by several eminent continental veterinary professors, and 
though, on the whole, their researches have tended to throw 
much light on the subject, yet it has not been completely 
elucidated ; the arrangement of the cells in the fibres has not, 
to my knowledge, been definitely explained ; their non-vital 
contents have not been made out, neither has the manner in 
which the fibres themselves are cemented into a solid mass 
been clearly shown ; in fact, so far as I can learn, very much 
relating to the histology of the hoof and the subjacent tissues 
has yet to be examined and explained. In the mean time 
I will endeavour to describe what my own researches have 
afforded in this respect, and I trust it will be found that 
our knowledge of the structure of such an important organ is 
largely increased, and many obscure or debatable points 
finally settled. 
Microscopically, we find the texture of the wall looser and 
less solid looking on its inner than its outer face. The 
fibrous tubes are somewhat larger, and are rounder or 
slightly oval in shape ; while the concentric lamellae are 
apparently more extensively disposed around them, from their 
want of compactness. Towards the outer surface this appear- 
ance changes ; the lamellae become more densely aggregated, 
as is shown by their closer markings and deeper tint, and 
they, with the canals, are greatly elongated on a plan with 
the direction of the wall. To display the structure of this 
compact mass of horn, chemical reagents are required, the 
most useful of which is caustic potash or soda.* 
When a minute portion of horn has been properly prepared, 
the cells are disunited and enlarged, and where previously 
nothing was observed but delicate lines with an almost 
transparent and apparently homogeneous substancef between, 
* In my investigations I have found a very expeditious method of display- 
ing the cellular arrangement of the hoof to be as follows The minute portion 
to be examined is put on the slide and covered by a rather large covering 
glass, which is retained by a small brass-wire clip. A drop or two of the 
potash, or soda solution, is then allowed to flow between the glasses, and the 
object is passed a few times quickly over the flame of a spirit lamp. The 
horn immediately swells out, becomes transparent, and the disposition of 
the cells can then be easily seen. 
f Professor Gourdon, of Toulouse, terms the interfibrous substance 
amorphous : “ Si, toujours a l’aide du microscope, on examine la corne du 
sabot prise en masse, on la voit entierment formee par uue substance 
amorphe traversee dans toute son djuasseur par une serie du tubulures 
