2$6 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 



Fig. 124.— ^Longitudinal Section of a Foot with Laminitis of 

 Three Weeks' Standing. 



On the anterior face of the cavity, in front of the os pedis, are 

 thickened horny laminae. Due to the sinking of the bony col- 

 umn the os pedis has perforated the horny sole. 



the horny laminae. 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 J inch to 1 inch 

 wide. Laterally it extends on each side of the toe to the 

 commencement of the quarters. 



Exploration with a director, or with the blade of a 



