7 
602 THE NERVOUS SYSTEM. 
OBTURATOR NERVE. 
The obturator nerve (n. obturatorius) supples the muscles and skin on the 
inner side of the thigh. It arises in the substance of the psoas muscle by three 
roots placed in front of those of the anterior crural nerve, and derived from the 
second, third, and fourth lumbar nerves (Fig. 440, p. 599). Sometimes the root 
from the second nerve is absent. Passing vertically downwards,'the nerve emerges 
from the psoas at its inner border, behind the common iliac, and on the outer side 
of the internal iliac vessels. It passes forwards below the pelvic brim in company 
with the obturator artery to the obturator groove of the thyroid foramen, through 
which it reaches the thigh. While in the obturator eroove it separates into its 
two main branches, named superficial and deep (Fig. AAT, p. 601). 
The superficial branch enters the thigh in front of the obturator externus and 
adductor brevis muscles, and beneath the pectineus and adductor longus. In the 
middle third of the thigh it is found coursing along the inner border of the adductor 
longus, anterior to the gracilis; and it finally divides into two slender terminal 
filaments, of which one enters Hunter’s canal and ends on the femoral artery, the 
other supplies the skin for a‘ variable distance on the inner side of the thigh and 
joins in the obturator (subsartorial) plexus. 
The branches of the superficial part of the nerve are :— 
1. An articular branch to the hip joint which arises from the nerve as soon as 
it eae the thigh, and supplies the joint through the acetabular notch. 
Muscular branches to the adductor longus, gracilis, adductor brevis (usually), 
Bada (occasionally). The last-named muscle is not usually supphed from the 
obturator nerve. 
A cutaneous branch of very variable size forms one of the terminal branches 
(Fig. 442). It becomes superficial between the gracilis and adductor longus, in the 
middle third of the thigh, and may supply the skin of the lower two-thirds of the 
thigh in its inner side. It is generally of small size, and is connected with 
branches of the internal cutaneous and’ internal saphenous nerves behind the 
sartorius muscle to form the obturator (subsartorial) plexus. The branch from the 
internal saphenous nerve to the plexus passes inwards behind the sartorius after 
piercing the aponeurotic covering of Hunter’s canal. The branch from the internal 
cutaneous nerve is generally superficial at the point of formation of the plexus. 
4. The branch to the femoral artery is the other terminal branch of the 
nerve. It enters Hunter’s canal along the inner edge of the adductor longus, and 
ramifies over the lower part of the artery. 
5. A fine communicating branch in front of the hip joint sometimes joins the 
anterior crural nerve. 
The deep part of the obturator nerve reaches the thigh by piercing the 
obturator externus muscle. It passes downwards between the adductor brevis and 
adductor magnus muscles. After passing obliquely through the adductor magnus, it 
appears in the popliteal space on the popliteal vessels, and terminates by piercing 
the posterior ligament and supplying the knee joint. 
Its branches are:—(1) muscular branches to the obturator externus, adductor 
magnus, and (when the muscle is not supplied by the superficial part of the nerve) 
the adductor brevis. The branch to the obturator externus arises before the 
nerve enters the muscle, in the obturator groove. The nerve to the adductor 
magnus is given off as the obturator nerve passes through the substance of the 
muscle. (2) An articular terminal branch is supplied to the back of the knee 
joint. 
ANTERIOR CRURAL NERVE. 
The anterior crural nerve (n. femoralis) is the great nerve for the muscles 
and skin of the thigh. It arises in the substance of the psoas muscle, from the 
back of the second, third, and fourth lumbar nerves, behind the obturator nerve. 
Passing obliquely through the psoas muscle, it emerges from its outer border in the 
false pelvis (Fig. 440, p. “599). Passing downwards in the eroove between the psoas 
and iliacus, it enters the thigh beneath Poupart’s ligament, external to the femoral 
