2 ANATOMY AND PHYSIOLOGY OP THE HORSE*S FOOT. 
salient tumour, projecting beyond the level of the other por¬ 
tions of the wall. No pressure or resistance having been 
exercised at this point, it would appear that the new material , 
has been more rapidly and abundantly poured out. Another 
evidence in favour of this suractivity of the keratogenous 
function is afforded in the direction which the fibres entering 
into the composition of this tumour affect. Longer than the 
space between the surface from which they emerged and the 
commencement of the vascular lamime over which they are to 
glide, these fibres have not the rectilinear direction of those in 
other parts of the wall, but describe an undulating curve 
outwards, and so adapt themselves to the short space in which 
they are enclosed. It is only at a later period, when they 
have become fairly associated with the horny laminae pro¬ 
duced at the lower margin of the coronary cushion, and are 
carried downwards by the ordinary movement excited by 
growth, that they assume a rectilinear form. 
As pointed out also by M. Bouley, the practice of farriery 
furnishes additional proofs of the great activity of the coronary 
cushion on those points of its surface where the horn in pro¬ 
cess of formation meets with least resistance. Thus, the 
growth of the heels is stimulated by paring them very thin 
and applying to the foot what the farriers designate a “ bar- 
shoe,” which removes them from weight-bearing, and in this 
way diminishes the pressure transmitted to the corresponding 
parts of the cushion. By this means it is sometimes possible 
to obtain, in what is vulgarly known as “ sandcrack ” (a 
fissure extending longitudinally in the wall, generally pene¬ 
trating to the living tissues), the formation of a continuous 
thick ring of horn, which in time takes the place of that 
which has become split; and it is also possible, by the 
methodical application of the same principles, to restore heels 
which have become too low or contracted to their proper 
height or normal diametrical development. It is also the 
same when the hoofs have grown so irregularly that one side, 
usually the inner, is higher than the other (or a travers, as 
the French veterinarians have it); by proper shoeing and 
adjustment of the hoof the weight may be thrown on those 
parts in which the growth of horn is most active, so as to 
lessen it; while the other region, which has sustained the 
undue amount of pressure that has caused it to suspend its 
secretion wholly or in part, may be so relieved as to resume 
its ordinary function again. 
The influence of unequal pressure on the horn-producing 
apparatus of the coronary cushion is in like manner well 
illustrated in that deformity of the foot in which the whole 
