hould now be divided,
between the mesial line and the semimembranosus, till the sheath of
the vessels be exposed. The sheath should be incised at its inner side,
to avoid wounding the popliteal vein. The pulsation of the artery will
now indicate its exact position. As the vein adheres firmly to the coats
of the artery, some care is required to separate the two vessels, so as
to pass the ligature around each end of the artery from without inwards,
while excluding the vein. While this operation is being performed in a
case of wound of the popliteal artery, the haemorrhage may be arrested
by compressing the femoral vessel, either against the femur or the os
pubis.

In the operation for tying the posterior tibial artery near its middle,
an incision of three or four inches in extent is to be made through the
skin and fascia, in a line corresponding with the inner posterior margin
of the tibia and the great muscles of the calf. The long saphena vein
should be here avoided. The origins of the gastrocnemius and soleus
muscles require to be detached from the tibia, and then the knee is to
be flexed and the foot extended, so as to allow these muscles to be
retracted from the plane of the vessels. This being done, the deep
fascia which covers the artery and its accompanying nerve is next to be
divided. The artery will now appear pulsating at a situation an inch
from the edge of the tibia. While the ligature is being passed around
the artery, due care should be taken to exclude the venae comites and
the nerve.

DESCRIPTION OF PLATES 65 & 66.

PLATE 65.

A. Tendon of the gracilis muscle.

B B. The fascia lata.

C C. Tendon of the semimembranosus muscle.

D. Tendon of the semitendinosus muscle.

E E. The two heads of the gastrocnemius muscle.

F. The popliteal artery.

G. The popliteal vein joined by the short saphena vein.

H. The middle branch of the sciatic nerve.

I. The outer (peronaeal) branch of the sciatic nerve.

K. The posterior tibial nerve continued from the middle branch of the
sciatic, and extending to K, behind the inner ankle.

L. The posterior (short) saphena vein.

M M. The fascia covering the gastrocnemius muscle.

N. The short (posterior) saphena nerve, formed by the union of branches
from the peronaeal and posterior tibial nerves.

O. The posterior tibial artery appearing from beneath the soleus muscle
in the lower part of the leg.

P. The soleus muscle joining the tendo Achilli