138 
anteriorly, with the fibula and _ interosseous 
ligament posteriorly, with the peroneus brevis 
on the fibular side, and with the extensor com- 
munis on the tibial side. Its tendon passes in 
the same sheath with that of the common ex- 
tensor, under the annular ligament. 
A very slight effort of the extensor com- 
munis and extensor proprius pollicis extends 
the digital pales and, if their action be 
continued, they will be made to bend the foot 
upon the leg. This they are enabled to do by 
the manner in which their line of direction is 
altered by the annular ligament of the ankle- 
joint, as it gives them all the mechanical ad- 
vantage of a pulley. The tibialis anticus and 
the peroneus tertius are the direct flexors of the 
foot on the leg, and if either act separately, it 
will give a’slight inclination towards the cor- 
responding side, and thus the last-named 
muscle forms one of that important set whose 
action is, by elevating the outer side of the 
foot, to throw the weight of the body on the 
inner side.* In the erect position these muscles 
take their fixed point below, and, by drawing 
on the bones of the leg, keep them perpen- 
dicular on the foot. 
The external muscles of the leg are two, the 
peroneus longus and brevis. They ye the 
whole length of the outer side of the fibula, and 
are placed between the extensors and flexors. 
1. Peroneus longus is a long powerful muscle, 
arising from a small portion of the fibular side 
of the head of the tibia, from the upper third 
of the outer side of the fibula, and from the 
fascia of the leg and its intermuscular pro- 
cesses. Proceeding obliquely downwards, the 
fibres are attached to a strong tendon, which 
passes, in contact with the peroneus brevis, 
along a groove at the back of the outer mal- 
leolus, enclosed in a synovial sheath. The 
tendon then passes through a rst | suleus in 
the cuboid bone, behind the base of the meta- 
tarsal bone of the little toe, winding obliquely 
across the sole of the foot, covered by the 
muscles of this part, till it is inserted into the 
internal cuneiform bone and base of the meta- 
tarsal bone of the great toe. In the tendon 
opposite the cuboid bone, is usually found a 
sesamoid bone. A bursal sheath encloses it in 
its passage across the foot. The action of this 
important muscle is to assist in extending the 
foot upon the leg, but principally to elevate 
the outer side of the foot, and thus regulate 
the bearing of the leg so as to throw the prin- 
cipal part of the weight upon the great toe.t 
This muscle is in contact on its outer side 
with the fascia of the leg. Indeed this apo- 
neurosis almost invests it, dipping between it 
and the flexor behind and extensors before. 
The peroneus is in contact with the fibula on 
its inner side above, lower down it rests upon 
the peroneus brevis. When passing across the 
foot it lies close to the bones, and conse- 
quently is covered by all the muscles of the 
sole. ; 
2. Peroneus brevis is situated at the outer 
* For further observations upon the action of the 
peronei muscles, see article FOOT, MUSCLES OF, 
+ See also Quain’s Manual of Anatomy. 
MUSCLES OF THE LEG. 
side of the leg, but lower down as to 
tachments than the preceding muscle. It a 
fleshy from the lower half of the outer side 
the fibula to near the outer malleolus, © 
sends offa roundish strong tendon, which pa: 
in the same groove behind the outer m 
lus, and in the same synovial sheath as the 
ceding muscle, but after passing the mal 
it has a sheath proper to itself. It is ins 
into the base of the metatarsal bone o 
little toe. Connected on its outer si 
peroneus longus, on the inner side to 
anteriorly to the common extensor and 
neus tertius, and posteriorly to the fi 
pollicis. : 
The action of these two muscles is f 
By the change in their direction, after tu 
behind the outer ankle, they are enabl 
ara the foot back, and so extend it o1 
eg. . 
The penoneus tertius is on the ec 
flexor ; it lies before the fibula, and ¢ 
in this action with the tibialis anticus to¢ 
the flexor. When, however, the three pe 
act together, and without the other flexors, 
combined action is to evert the sole of the 
and thus counterbalance the effect of the: 
ness of the outer side of the foot by t 
ferring the superincumbent weight to the | 
side. This action is particularly exemp 
in skaiting, but it is essential to every m 
ment of ordinary progression. (See a 
Foor, Muscies or.) When the foot is 
fixed point, the peronei act by keepin 
fibula and the whole leg steady, and — 
in the act of standing on one foot, cou 
acting the tendency of the body to fal 
wards. wall 
The posterior region of the leg com 
seven muscles, six of which are acting on 
foot and toes, and one is proper tot 
joint. We shall examine them as they ai 
with in dissection, and shall therefore dese 
them as forming two layers, superficial 
deep. The tirst contains three muscles: 1, 
trocnemius ; 2. soleus; 3. plantaris, __ 
1. Gastrocnemius.—This is situated it 
diately under the aponeurosis, and is a pt 
ful muscle, broad and flat anteriorly, and 
vex posteriorly, and forming the gre: 
of what is called the calf. It arises 
distinct heads from the back and upp 
of the two condyles of the femur, of 
the inner is the longer, and somewhat la 
These heads have between them a bi 
sulcus, which forms the lower of 
liteal space. They unite a little b 
knee-joint, in a middle tendinous line 
below the middle of the tibia send off g 
tendon which unites with the tendon 
soleus, a little above the ankle. ‘ 
The posterior surface is covered by the 
of the leg ; anteriorly it rests upon the 
teus, soleus, and plantaris, and poy 
vessels. When its heads pass over the ¢ 
dyles of the femur, they are guarded by sy 
burse. te 
2. Soleus.— This is the second porti 
that great muscle of the leg which has 
. 
