064 
ANATOMY OF THE HORSE. 
flattened; and this admits of the adaptation of their surfaces to 
each other. In their passage down the leg, they are connected 
together and invested by cellular tissue: a loose cellular sub¬ 
stance also connects them to the suspensory ligament and 
cannon bones. The perforans tendon at the back of the fetlock 
spreads again in breadth, and re-assumes a cartilaginous texture, 
and is likewise (the same as at the knee) surrounded by a syno¬ 
vial sheath, formed principally by the tendo perforatus; from 
which it only emerges at the division of the latter. Opposite 
to the os coronse it is destitute of any tendinous covering, and 
is invested by cellular membrane only. It next sinks into the 
substance of the frog, passing over the navicular bone, where 
it becomes cartilaginous, and adapted in shape to the posterior 
articular surface of that bone, a bursa or circumscribed syno¬ 
vial cavity existing between them. Finally, it ends in an ex¬ 
panded termination which is broadly implanted into the posterior 
concavity of the os pedis. 
Action .—To bend the foot. It will also assist in the flexion 
of the pastern, fetlock, and leg. 
radialis accessorius. — Flexor accessorius . 
Situation .—Deep-seated, along the infero-posterior side of the 
arm. 1 * n 
Figure .—Irregular; short; flattened: upper part, bifurcate. 
Attachment .—Superiorly, mesio-posterior part of the radius: 
inferiorly, its tendon joins that of the perforans. 
Relations .—Anteriorly, with the radius ; posteriorly, with the 
bellies of the perforatus and perforans: internally, with the radial 
blood-vessels and nerves. 
Direction .«—From above dowmwards, inclining in a sort of 
curve from without inwards. 
Structure .—It has two beginnings. One is pyramidal, elon¬ 
gated and tendinous, and extends high up the radius: the other 
is triangular and fleshy, and is attached lower down. They both 
unite to form one fleshy belly, which is intermixed with slips of 
tendon, and finally ends in a single narrow flaettned tendon. 
Action .—To assist the perforans. 
lumbrici, anterior et posterior. — Lumbricales. 
Consist of two pairs of pale, delicate, small muscles, having 
long slender tendons. 
The lumbrici posteriores are to be found invested in adipose 
membrane, adhering to the inner side of the tendo perforans, 
about one-third of its length upwards from the fetlock. Here- 
