48 THE ELASTIC TISSUES OF THE FOOT. 



same direction as the anterior, is sharp, and exhibits a number 

 of depressions, through which vessels pass. The antero-superior 

 angle is formed by the meeting of the anterior and upper borders. 

 It is attached to the lateral surfaces of the coronet bone by 

 strong ligaments (figs. 29, h, and 30, c). The antero-inferior 

 angle is connected with the wing of the os pedis. The postero- 

 superior angle, formed by the meeting of the upper and posterior 

 borders, is somewhat rounded off. The postero-inferior angle 

 is connected with the plantar cushion. 



A short note on ossification of the lateral cartilage may 

 perhaps be permissible. Lungvvitz's experiments showed that 

 of 1251 animals examined, 11*5 per cent, had well-marked 

 ossification. Lungwitz states that side-bone is commonest in 

 heavy, coarse-bred horses (our common experience) ; the fore- 

 feet are most frequently affected — the left foot more commonly 

 than the right, and -the outer cartilage oftener than the inner. 

 Ossification may occur early in life, especially at the time 

 when animals are first put to work. Well-bred animals 

 seldom suffer. 



2. The Plantar Cushion. 



The fibro-fatty frog or plantar cushion (figs. 31, a, and 10, i), 

 althouoli sometimes described as consistinf^ of two different 

 parts, the sensitive bulbs and sensitive frog, must practically 

 be regarded as one and indivisible. It is diflicult to find an 

 object which precisely simulates it in form ; but it may be 

 compared to a wedge whose sides all converge to one point, or 

 to a four -sided pyramid, one surface of wdiich is slightly convex, 

 the opposite concave. 



The convex, thicker end of the plantar cushion, is turned 

 towards the rear, and is surrounded by the posterior part of 

 the lateral cartilage. Thence it converges to a point correspond- 

 ing in position to the border between the anterior and middle 

 thirds of the lower surface of the pedal bone. Consequently, 

 it covers the centre of the two posterior thirds of the sensitive 

 foot. 



The postero-superior part (figs. 31, a, 32, a, 33, a, and 34, V) is 

 convex, rounded, and rises on either side above the neighbouiing 

 portions. Its centre is marked by a slight depression, dividing 



