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THE MUSCLES ON THE FRONT OF THE THIGH. 343 
half of the linea aspera and upper part of the line leading therefrom to the 
external condyle, as well as (5) from a corresponding portion of the external 
intermuscular septum. 
For the most part deeply placed, the muscle is directed downwards to an 
insertion into the deep surface of the tendons of the rectus and vasti muscles by 
means of fibres which join a membranous expansion on its surface. 
The crureus is concealed by the rectus and vasti muscles, and by the ilio- 
tibial band externally, in the lower half of the thigh. It is closely adherent to the 
vastus externus muscles in the middle third. of the thigh; it is inseparable from 
the vastus internus below the upper third. Beneath the crureus is the femur; 
and in the lower third of the thigh it conceals the subcrureus muscle, a bursa, and 
the upward prolongation of the synovial membrane of the knee-joint. 
The subcrureus consists of a number of separate bundles of muscular fibres 
arising beneath the crureus from the lower fourth of the front of the femur, and 
inserted into the synovial membrane of the knee-joint beneath the tendon of the 
rectus femoris. 
The four elements composing the quadriceps extensor muscle have been traced 
in their convergence to the patella and the lateral ligaments of the patella, 
Their ultimate insertion is into the tibia, by means of the ligamentum patella, 
and the lateral ligaments of the patella. The patella, indeed, is in one sense a 
_sesamoid bone formed in the tendon of the muscle, the ligamentum patelle being 
the real tendon of insertion, and the lateral ligaments fascial expansions from 
its borders. The insertion of the muscle forms the front of the capsule of the 
knee-joint, 
The ilio-psoas muscle is a compound muscle, consisting of one or sometimes 
two elements (psoas, magnus and parvus) connecting the femur and pelvic girdle to 
the axial skeleton ; and another element, the iliacus, extending between the pelvis 
and the thigh, The muscles chiefly occupy the posterior wall of the abdomen 
and false pelvis, their insertions only appearing in the thigh below Poupart’s 
ligament. 
The psoas magnus (m. psoas major) is a large pyriform muscle, which has an 
extensive origin from the vertebral column in the luinbar region. It arises (1) 
from the intervertebral discs above each lumbar vertebra, and from the adjacent 
margins of the vertebre—from the lower border of the 12th thoracic to the upper 
border of the 5th lumbar vertebra; (2) it arises also from four aponeurotic arches 
which pass over the sides of the bodies of the first four lumbar vertebree ; and (3) 
it has an additional origin posteriorly from the transverse processes of all the 
lumbar vertebrae. The fibres form a fusiform muscle directed downwards over the 
pelvic brim and beneath Poupart’s ligament, ending in a tendon which is inserted 
into the apex of the lesser trochanter of the femur. 
The psoas muscle occupies the posterior abdominal wall, the false pelvis and 
the thigh. In the abdomen it lies in the groove alongside the bodies of the lumbar 
vertebrae, in front of the transverse processes, and enveloped by a fascia derived 
from the lumbar aponeurosis. The abdominal viscera in contact with it are: 
the kidney and colon on both sides, with the duodenum on the right, and the 
pancreas on the left side. The ureter is in front of it, along with the spermatic 
or ovarian, the renal and colic vessels. The inferior vena cava is in front of the 
right muscle; the inferior mesenteric vein is in front of that of the left side. The 
lumbar plexus is imbedded in its substance, and the nerves of distribution emerge 
from its borders and surface. In the false pelvis the psoas covers the pelvic brim, 
and is covered by the ureter, the iliac vessels, the ileum on the right side, and the 
iliac colon on the left side. The vas deferens and spermatic vessels cross over 
it just above Poupart’s ligament. In Scarpa’s triangle the tendon is behind the 
femoral vessels, between the iliacus and pectineus, and in front of the obturator 
externus muscle and the hip-joint. A bursa, which may be continuous with the 
synovial cavity of the hip-joint, separates the tendon from the pubis and the capsule 
of the hip-joint. 
The psoas parvus (m. psoas minor) is often absent (40 per cent). It arises 
from the intervertebral disc between the last thoracic and first lumbar vertebre, and 
