DISEASES OF THE BONES 397 
_ upon the pedal bone. As a result there is a marked de- 
pression at the coronet, the depression being heightened 
in effect by the exostosis in front. Pyramidal disease is, 
as a rule, met with in the hind-feet, but occurs also in 
the fore. 
Pathological Anatomy.—When occurring without fracture, 
the first observable change is a thinning of the articular 
cartilage of the pyramidal process, through which the bone 
beneath appears abnormally white. Later the thinning of 
the cartilage progresses until at last it becomes entirely 
obliterated. This destruction of the cartilage commences 
first at the highest point of the articular surface of the 
pyramid, and gradually reaches further backward into the 
joint. While this is taking place the new bone is being 
formed on the front of the os pedis, below and around the 
process, until, as we have already seen, an exostosis is 
formed, Jarge enough to be noticeable at the coronet. 
This, of course, partly implicates the joint and the points 
of the insertion of the extensor tendon. 
Finally, fracture may, or may not, take place. When it 
does the exostosis is larger, and the general deformity of 
the hoof greater. 
Treatment.—Ordinary treatment, such as point or line 
firing, repeated blisters, or hoof section, each of which we 
have tried, appears to be utterly useless. So far as we 
have been able to gather from the writings of other prac- 
titioners, however, neurectomy returns the animal for a 
time to usefulness. If the fore-limb is the seat of trouble, 
either plantar or median neurectomy may be practised ; if 
the hind, then the best results are obtained by section of 
the posterior tibial. 
Reported Cases.—1. ‘This animal, a mare, had been 
rested for lameness behind for two or three weeks, and 
then sent out to work, going sound. This was repeated 
several times, and each time the coachman reported, ‘‘ Goes 
very lame behind after she has been at work about fifteen 
to twenty minutes.” She always pulled out sound when I 
saw her in a halter on the following day, so I had her 
