THE FOOT OF THE HOESE. 43 



Two of these flex or bend the joints while the other straightens 

 the column of bones thus displaced. The superficial flexor of 

 the foot is the flexor perforatus, which is attached to the sides of 

 the lower pastern-bone and flexes the ankle at the fetlock. The 

 deep flexor of the foot is the flexor perforans, inserted into the 

 bottom of the cofiin-bone, whence it bends the cofiin-joint and 

 with it the whole foot. The front extensor tendon of the foot 

 is attached to the pyramidal process of the coffin-bone. There 

 are many other minor muscles, fixed and movable, connected 

 with the cannon, splints, and other bones of the limb, which as- 

 sist in the various movements and in their degree relieve the 

 controlling muscles of a share of the stress of weight, as well as 

 of whatever force or stain is brought to bear upon them. See 

 Fig. 4 and colored plates. 



Soft Tissues. — The bones, ligaments and muscles of the 

 foot are covered by a loose connective tissue, which gives sym- 

 metry to the parts, and all are protected by the external cover- 

 ing of skin and horn tissues, I have already mentioned that in 

 connection with the coffin-bone there is a supplementary appa- 

 ratus of cartilage formation. This is composed of two lateral 

 pieces, representing a thin flat plate on each side, of a fibrous 

 elastic substance, pierced with openings for the passage of veins 

 and nerves of the digital region. They are united behind and 

 below to the plantar cushion, and in front cover the articulation 

 of the coffin-joint and synovial sac, blending into the ligaments 

 at that point. These cartilages are adapted to act as pads in 

 easing shocks caused by exertions of the foot, but it often 

 happens that they undergo changes and are invaded by an 

 ossifying process which converts them into bone, as explained 

 in a subsequent chapter. 



The coronary cushion is a continuation of the skin and 

 forms an intermediate juncture between it and the wall of the 

 hoof, of which it is the matrix. It occupies a groove, called 



