432 
ON COllON 1T1S. 
creation. Had the edge of the crust been as plentifully supplied 
with secretion as the upper portions, it would not have been fitted 
for its especial character of toughness, which renders the foot in a 
natural state capable of sustaining a great amount of wear without 
either breaking or consuming too rapidly. I may here be allowed 
to make a remark on the imperfect views which have been taken 
of the effects of greasy applications on the one hand, and of water 
on the other. In a state of health, neither water nor grease has any 
effect upon the living horn, as they never penetrate into its sub- 
stance. Water keeps the surface in that softened state which 
facilitates the evaporation of the perspiratory secretion, and thus 
leaves the horn harsh and brittle from the mere evaporation of its 
juices, which is but slight so long as the horn is protected by its 
natural epidermis ; but when it is deprived of this by the false 
principle of adding to beauty of appearance by rasping it away, 
then the consequences are much more injurious.* Grease or oil, 
under either circumstance, do not penetrate the substance, and 
render it soft and crumbling, or rotten, as is generally supposed, 
but by closing the surface of the horn, which is naturally intended 
to exude, though in a very slight degree, prevents the evaporation 
of the more fluid portion, which, unable to permeate the horn, 
remains to act upon it, and simply by action of its own constituents 
is destroyed. Thus, what is hurtful under a state of health will not 
prove so under a derangement of function ; but this very effect 
will be found of great benefit in retaining that secretion which is 
requisite for the performance of its functions. Grease, oil, tar, 
water impregnated with common salt, sulphates of the metals, and 
various other substances, have the effect of rendering impervious 
the surface of the horn, and thus preventing the evaporation. That 
none of these various articles, or water alone, ever penetrate into 
living horn, is shewn daily in every forge. Examine a foot that 
has been stopped with common tar ointment, and it will be found 
to have penetrated only so far as there may be a portion of dead 
horn, but not the slightest portion will have entered into the living 
horn. Apply to the crust any of the preparations of tar, even the 
Barbadoes naphtha, the most penetrating thing that 1 am acquainted 
with, they will never penetrate so deeply, but that a scrape of the 
finger-nail will expose the horn unstained. 
An examination of the coronary body will shew two sets of 
vessels upon the surface, one villous, the other elongated. The vil- 
lous secrete the horn ; the elongated are placed singly but regularly 
over the surface; the greatest number, however, are in the centre; 
these shoot into the substance of the horn, and, from their extremi- 
ties, the tubular fibres emanate : and these are, 1 believe, for the 
purpose of keeping the horn elastic, by distilling, as it were, a fluid 
