286 DISEASES OF THE HORSE’S FOOT 
horn composing it takes on an abnormal growth at the toe 
(see Fig. 123). This adds still further to the abnormal 
lengthening of the antero-posterior diameter of the foot 
already mentioned. 
In other cases horn in this position is altogether wanting, 
and in its place is a well-defined cavity, into which the 
blade of a knife can be readily passed. This cavity is 
bounded in front by the original wall of the hoof, and is 
here lined by a degenerated and hypertrophied growth of 
Fie. 124.—Lonerrupinat Secrion or a Foor wir LamMINrvTIs oF 
THREE WEsKs’ STANDING. 
On the anterior face of the cavity, in front of the os pedis, are thickened 
horny lamine. Due to the sinking of the bony column, the os pedis has 
perforated the horny sole. 
the horny lamine. Posteriorly the cavity is bounded by 
the front of the os pedis, and is lined by a thin growth of 
horn secreted by the keratogenous membrane covering the 
bone. Superiorly the cavity is quite narrow, and extends 
to near the lower surface of the coronary cushion, while 
inferiorly, at its open portion, it is often } inch to 1 inch 
wide. Laterally it extends on each side of the toe to the 
commencenient of the quarters. 
Exploration with a director, or with the blade of a 
