532 DR. J. MURIE ON THE ANATOMY OF THE SEA-LION. 
c. Of Loins and Hind Limb.—Lumbar plexus. Hidden entirely by the psoas muscle 
and not lying upon but issuing from behind the quadratus lumborum, the lumbar 
nerves partly are superimposed and partly dip beneath the iliacus, but, relatively to the 
sacral nerves, are small. 
The external cutaneous nerve sends filaments to the rectus femoris, vastus mternus, 
and crureus, and passes down transversely over the thigh; superficial to the pectineus 
and adductors longus and magnus it is distributed to the fascia and skin at the middle 
and inner side of the shaft of the tibia. 
The muscular branches of the femoral nerve in the groin are distributed to the 
crureus, vastus internus, and both divisions of the adductor longus and magnus. ‘The 
femoral nerve accompanies the artery through the opening in the adductor magnus 
muscle. With regard to the obturator nerve, I include it with the sacral plexus, to 
which in this case it more properly belongs. 
Sacral Plexus.—This (with junction to lumbo-sacral) is composed of three large 
trunks, which emerge from as many of the anterior sacral foramina. ‘The first of these 
trunks immediately on its exit sends off a branch which joins the posterior deep nerves ; 
the main trunk then goes backwards to opposite the next sacral foramen, where it 
splits into two nearly equal-sized branches: the shorter one (0°2 inch) unites with the 
second sacral nerve; the longer one forms the obturator nerve, which proceeds under 
cover of the pelvic fascia to the anterior border of the obturator internus, and pierces 
it. The second sacral nerve is rather thicker than the first; it unites with the third 
at the narrow portion of the pelvis, and there forms a thick single trunk, which passes 
through the great ischiatic notch. From each sacral nerve a small branch is sent 
inwards and backwards, which communicates through a ganglion impar with a twig 
from the sympathetic sacral nerves. ‘The nerve is continued backwards from the gan- 
glion, and, with the other minute caudal twigs, supplies the muscles and viscera within 
the pelvis. 
As the sacral plexus passes round and out of the great ischiatic foramen (here consi- 
derably narrowed) it bears relation to the parts as follows:—From within outwards it 
lies upon the gemellus inferior, the hinder part of the quadratus femoris, the long 
adductors and the semimembranosus. Above or dorsally it is covered by the levator 
caude externus, the first and the second portions of the gluteus maximus, the sacro- 
peroneus muscle, and the broad biceps. ‘The gluteal artery and vein, as usual, accom- 
pany the nervous plexus. 
The lesser ischiatic nerve comes off at the outer border of the quadratus femoris, 
after traversing the great sacro-ischiatic notch with the great ischiatic nerve and vessels. 
It afterwards lies on the semitendinosus and on the surface of the soleus, being covered 
by the semimembranosus, the sacro-peroneus, and second portion of the biceps. It 
proceeds as far as the heel. 
The external popliteal or peroneal nerve proceeds in a slanting manner outwards and 
