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, large 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 



