[Illustration:  FIG. 154, 155—­EFFECTS OF PERIOSTITIS ON THE OS PEDIS.]

’Post-mortem reveals the small nodular growths on the inner surfaces of the wings of the pedal bone, and if long established the ends of the navicular bone are also involved.  Exudation and gradual growth of false material around the nodules takes place, which also serves to increase pressure.’[A]

[Footnote A:  Captain L.M.Smith, A.V.D., Veterinary Record, vol. xi., p. 229.]

3.  ’This case was brought for my opinion.  The horse was lame, and walked similar to one that had had laminitis, putting the heel down first upon the ground.  I ordered the patient to be destroyed.  You will note the ossification of the flexor pedis at its attachment to the pedal bone.  I enclose photos of the ground, also of the articular, surfaces of the bone.’[A]

[Footnote A:  F.B.Jones, M.R.C.V.S., Veterinary Record, vol. xi., p. 230.]

B. PYRAMIDAL DISEASE, BUTTRESS FOOT, OR LOW RINGBONE.

Definition.—­A condition of periostitis and ostitis in the region of the pyramidal process of the os pedis, usually preceded, but sometimes followed, by fracture of the process, and characterized by deformity of the hoof and an alteration in the normal angle of the joint.

Causes.—­In the majority of cases buttress foot is brought about by fracture of the pyramidal process.  Thus, although distinct evidence of such is nearly always wanting, we may assume that the original cause is violent injury to the part in question.  Properly, therefore, one would say that this condition should be described under Fractures of the Os Pedis.  It appears, however, that other cases of the kind arise in which fracture is altogether absent, or in which it is plainly seen to be subsequent to the diseased processes in the bone.  For that reason, and also for the reason that the condition has come to be known by the name we have given, we give it special mention.

Symptoms and Diagnosis.—­Even when the condition arises as the result of fracture, the ordinary manifestations of such a lesion are absent.  By reason of the situation of the parts within the hoof we are unable to detect crepitation, and the resulting lameness is perhaps—­in fact, nearly always is—­neglected until such time as any heat or swelling caused by the injury has disappeared, in which case we are denied what evidence we might have obtained from that.  All that is presented is lameness, and lameness that is at times excessive.  But with the lameness there is nothing distinctive.  The foot is tender on percussion, and the gait suggestive of foot lameness, that is all.  We are unable, therefore, to make an exact diagnosis, and the condition goes for some time undetected.