EQUIDE 393 
but the principal metatarsal is more laterally compressed at its 
upper end than is the corresponding metacarpal. The joint 
between the femur and tibia, corresponding to the knee of man, is 
called the “stifle joint”; while that between the tibia and tarsus, 
corresponding to the ankle of man, is termed the “hock.” The 
bones and joints of the foot have the same names as in the fore 
limb. The Horse is eminently “digitigrade,” standing on the ex- 
tremity of the single digit of each foot, which is kept habitually in 
@ position approaching to vertical. 
The muscles} of the limbs are modified from those of the ordi- 
nary mammalian type in accordance with the reduced condition of 
the bones and 
the simple re- 
quirements of 
flexion and ex- 
tension of the 
joints, no such 
actions as pro- 
nation and 
supination, or 
opposition of 
digits, being 
possible or 
needed. The 
muscles, there- 
fore, which per- 7 
form these 
functions in 
other mammals 
are absent or 
rudimentary. 
Below the 
carpal and tar- 
sal joints the 
fore and hind 
limbs corre- 
spond almost 
Fic. 164.—Section of foot of Horse. 1, Metacarpal bone; 2, first 
phalanx (0s suffraginis); 3, second phalanx (os coronce); 4, third or 
ungual phalanx (0s pedis, or coffin-bone); 5, one of the upper sesamoid 
bones; 6, lower sesamoid or ‘‘navicular” bone; 7, tendon of anterior 
extensor of the phalanges ; 8, tendon of superficial flexor (fl. perforatus) ; 
9, tendon of deep flexor (jl. perforans); 10, suspensory ligament of 
fetlock; 11, inferior or short sesamoid ligament; 12, derma or skin 
of the foot, covered with hair, and continued into 18, the coronary 
cushion, 14, the podophyllous or laminar membrane, and 15, the kera- 
togenous membrane of the sole; 16, plantar cushion ; 17, hoof; 18, fatty 
cushion of fetlock. 
exactly in struc- 
ture as well as function. On the anterior or extensor surface of 
the limb a powerful tendon (7 in Fig. 164), that of the anterior 
extensor of the phalanges (corresponding to the extensor communis 
digitorum of the arm and eatensor longus digitorum of the foot of man) 
passes down over the metacarpal bone and phalanges, to be inserted 
mainly into the upper edge of the anterior surface of the last phalanx 
1 Want of space and of the necessary illustrations rendered it impossible to 
give an account of mammalian myology in the earlier chapters of this work. 
