INDIVIDUAL VARIATION.--The muscle is usually somewhat fused to the posteroproximal and anteroproximal fleshy corners of the underlying M. extensor iliofibularis. =_M. Extensor Iliotibialis Anticus_= (M. sartorius), Figs. 12, 13 _T. pallidicinctus_ GENERAL DESCRIPTION AND RELATIONS.--Anteriormost muscle of thigh; long and strap-shaped; proximal part entirely anterior (adjacent) to M. extensor iliotibialis lateralis; posterior edge of middle part medial to latter muscle; distal part mostly medial to Mm. extensor iliotibialis lateralis and vastus medialis; proximal part aponeurotic, continuous posteriorly with anteroproximal aponeurosis of M. extensor iliotibialis lateralis; anterior edge of M. extensor iliotibialis lateralis bound by strong connective tissue to adjacent part of M. extensor iliotibialis anticus; some fusion of fibers (proximally) between these two muscles; anteroproximal corner of fleshy part of muscle sometimes fused to underlying anterior edge of ilium and fascia covering body wall musculature adjacent (anterior) to ilium. ORIGIN.--The muscle arises aponeurotically from the anterior part of the anterior iliac crest and (anteroproximal corner) from the anterior end of the median dorsal ridge. INSERTION.--The flat tendon, continuous posteriorly with the superficial tendon of M. femoritibialis internus, fuses to the tendon of M. vastus medialis, contributing superficially to the medial part of the patellar tendon, which attaches to the medial half of the rotular crest; most of the tendon is overlapped by the edge of M. gastrocnemius pars interna. INNERVATION.--A branch of the anterior division of the femoral nerve gives twigs into the lateral surface of the posterior part. INDIVIDUAL VARIATION.--In two legs, a twig from the anteriormost branch of the middle division of the femoral nerve anastomoses with the typical branch to M. extensor iliotibialis anticus. _T. cupido_ INDIVIDUAL VARIATION.--In several legs, the anterior edge of origin extends forward onto the neural spine of the last free thoracic vertebra. A twig from the middle division of the femoral nerve anastomoses with the typical branch to M. extensor iliotibialis anticus in three legs. _P. p. jamesi_ DIFFERENCES FROM TYPICAL _T. pallidicinctus_.--There is no fusion of fibers between M. extensor iliotibialis anticus and M. extensor iliotibialis lateralis. INDIVIDUAL VARIATION.--The anterior edge of origin extends forward onto the neural spine of the last free thoracic vertebra in some legs. [Illustration: FIGURE 20. Explanation on opposite page.] EXPLANATION OF FIGURE 20 A-D. Dorsal views of M. iliotrochantericus medius, showing its relationship to femoral notch. × 1. In D, note absence of femoral notch and location of branch of femoral nerve. A. _Tympanuchus pallidicinctus_ 2L. B. _T. cupido pinnatus_ 4L. C. _Pedioecetes phasianellus jamesi_ 1L. D. _T. pallidicinctus_ 3L.