354 ANATOMY AND PHYSIOLOGY OF THE HORSE^ FOOT. 
ensure unity of motion ; and it also receives what is called an 
aponeurotic band that extends from the inner face of the wide 
pedal cartilage across the surface of the tendon, mixing its 
fibres closely with it. Finally, when it arrives at the pyramidal 
process of the os pedis, it is a broad but thin fibrous web 
encircling a large portion of the joint of the foot, and becomes 
implanted into the anterior face of that process (fig. 7, b ) 
by diverging fibres. 
The deep flexor tendon of the foot (fig. 7,f), when it has 
passed over the back of the fetlock and reached the coronary 
bone, also becomes transformed from a round to a flattened 
shape, to adapt itself to the particular requirements of this 
region. Without diminishing much in thickness, it never- 
theless widens out gradually into a broad band, which, at its 
termination (figs. 8, g ; 9, d ), has breadth enough to fill the 
space between the wings of the pedal bone, into the semi- 
lunar ridge of which it is implanted. In its course from the 
fetlock to the plantar surface this important tendon forms 
adhesions, or is more or less connected, with bones and 
fibrous structures, which still more intimately ally it with 
the functions of this region, enhance its powers of flexion, 
and render it at the same time a source of additional strength 
to the joints behind which it passes. In this way it is first 
maintained in close apposition against the pulley-like gliding 
surface behind the small coronary bone, by a fibrous sheath 
that passes around and binds together the two branches of 
the perforatus tendon, near their insertions into that bone 
(fig. 8, s). This gliding surface (fig. 3, k) is covered by a 
fibro- cartilaginous and a synovial membrane, and shows a 
beautiful and more or less complete arborisation of vessels 
over its entire face. Behind the lower end of the large pas- 
tern bone, and commencing by some bundles of fibres that 
spring from the synovial sheath through which the tendon 
passes, this cord receives the insertion of a ligament or mem- 
brane mainly or entirely composed of yellow elastic tissue. 
This membrane is at first very thin, but soon covers the face 
of the tendon as it glides behind the upper end of the second 
phalanx, and increases in thickness to a notable degree. 
Below the gliding surface it abruptly leaves the tendon, and 
implants itself into the middle of this phalanx and the upper 
border of the navicular bone (fig. 3, / m), not only connecting 
these very closely, but also forming a septum between the 
capsule of the foot-joint and the extensive tendinous bursa 
behind and above it. This yellow elastic ligament is in ap- 
pearance markedly different from the tendon, being of a dull 
yellowish hue, and in texture fine and close. Joining the 
