2IO ATLAS AND TEXT-BOOK OF HUMAN ANATOMY. 



of the posterior surface are arranged in two layers, the superficial one being formed by the tri- 

 ceps sura and the deep one consisting of the poplilcus, the tibialis posterior, the flexor digitorum 

 longus, and the flexor hallucis longus. The anterior group is composed of the tibialis anterior, 

 the extensor digitorum longus, the peronceus tertius, and the extensor hallucis longus. The exter- 

 nal group is formed by the peronceus longus and brevis. 



The muscles of the foot may be divided into the muscles of the dorsum and the muscles of 

 the sole (plantar muscles). The muscles of the dorsum are the extensor digitorum brevis and the 

 extensor hallucis brevis. The muscles of the sole are composed of a median group, the flexor 

 digitorum brevis and the quadra tus plantce; of a group passing to the great toe, the abductor hal- 

 lucis, the flexor hallucis brevis, and the adductor hallucis; and of a group passing to the little 

 toe, the abductor digiti V, the flexor brevis digiti V, and the opponens digiti V. The lumbricales 

 and the interossei are also situated in the sole of the foot. 



THE MUSCLES OF THE HIP. 

 THE INTERNAL MUSCLES OF THE HIP, THE ILIOPSOAS. 



The iliopsoas (Figs. 252, 296, 297, 299, and 300) is composed of the psoas major and the 

 iliacus, which are completely separated in the upper portion of their course but united at their 

 insertion. This muscle frequently also includes a psoas minor. 



The psoas major is a long, strong muscle, the greater portion of which is situated in the 

 posterior abdominal wall. It arises from the upper and lower margins of the bodies of the twelfth 

 thoracic to the fourth lumbar vertebras, from the intervertebral fibrocartilages, and from the 

 tendinous arches which pass over the concavities of the middle of the bodies of the lumbar verte- 

 brae and the lumbar vessels. A second series of origins comes from the transverse processes of 

 all of the lumbar vertebrae, but is concealed by the fibers proceeding from the vertebral bodies, 

 and the nerves forming the lumbar plexus pass between the two origins of the muscle. 



The muscle is flat above but becomes narrower and thicker as it passes downward and out- 

 ward over the terminal line of the pelvis and beneath the inguinal ligament to unite with the iliacus. 



It lies upon the lateral surfaces of the upper and middle portions of the lumbar vertebral 

 column and its upper portion is bridged over by the internal lumbocostal arch of the diaphragm. 

 The outer margin of the muscle is in relation above with the quadratus lumborum, which it partly 

 conceals, and below with the inner margin of the iliacus. The inner margins of the two psoas 

 major muscles form the lateral boundaries of the pelvic inlet. 



The iliacus is a flat, thick, strong muscle which fills the entire iliac fossa. It arises from the 

 iliac fossa, extending upward to the crest of the ilium and forward to the anterior superior and 

 inferior spines, and passes downward and forward behind the inguinal ligament and fuses with 

 the psoas major. 



The combined iliopsoas passes beneath Poupart's ligament through the muscular lacuna 

 (see page 231) into the thigh, where it is placed between the rectus femoris and the pectineus 

 and forms a deep fossa with the latter muscle, the ilio pectineal fossa. It runs directly over the 

 capsular ligament of the hip-joint, passes slightly backward, and is inserted by a short tendon 

 into the lesser trochanter. Where the muscle runs over the iliofemoral ligament of the hip- 



