30 
AN ESSAY ON CHRONIC PODOTROCHOLITIS. 
but that the occult variety most frequently produces the disease, 
because it exercises a strong degree of compression upon the coffin 
bone and the navicular, producing an elevation of the first of these 
two bones. Goodwin* agrees with Turner respecting the rest in 
the stable, but does not consider contraction of the hoof to be the 
cause of navicular disease, but that it arises from a diminution or 
total loss of the elasticity of the frog ; whence results a contusion of 
the perforans tendon between the frog and the navicular. He adds, 
that all horses, when in repose, like to have the pasterns elevated, 
and this position favours the ascent of the frog and sole ; and that 
as these two component parts of the hoof are found to have assumed 
a fixed position in consequence of prolonged rest, it needs but a 
gallop over the pavement to produce contusion of the tendon and 
chronic podotrocholitis. 
There is no doubt that prolonged rest in the stable is pre- 
judicial to the good qualities of the hoof, and may contribute to 
induce a diminution of the elasticity of the horn, especially as inac- 
tivity prevents to a greater or less degree the beneficial effects of 
alternate contraction and expansion ; nevertheless, it is the high 
temperature of the stables, and the dryness of the walls of the 
hoofs, which are more potent causes of the contraction and annihi- 
lation of the elasticity of the frog, than the prolonged rest upon 
which Goodwin and Turner lay such stress. Farmers’ and peasants’ 
horses are generally confined to the stable during the greater part 
of the winter, but the hoof is kept sufficiently soft to prevent all 
possibility of contraction taking place. 
The ascent of the frog, admitted by Goodwin as the consequence 
of prolonged repose, actually does take place ; the fatty frog first 
is elevated, and consequently draws the horny frog up with it : this 
is particularly observable in horses that stand over, and in such as 
are upright upon their pasterns. In this position, the suspensory 
ligament of the pastern causes the elevation of the entire fatty frog. 
If, to the already mentioned defects in the normal perpendicularity 
of the limb, be added circumstances which favour the drying of the 
hoof, it is evident that the elevation of the frog will become per- 
manent, and that, if these causes are prolonged, it will in the end 
lose all power of recovering its natural position. I shall not 
stop to combat the singular opinion of Turner, that the bone of the 
foot changes its place, and approaches nearer to the coronet: 
there is no question of an actual displacement of this bone, and I 
deem it superfluous to inquire into the causes of it. 
I divide the CAUSES of chronic podotrocholitis into predisposing 
and occasional. To the former belong the execution of the func- 
* Veterinarian, vol. iii. 
