ANATOMY IN A NUTSHELL. 141 



upper part of its internal prolongation below. The internal portion of the mus- 

 cle, consisting principally of those fibers which arise from the tuberosity of the 

 ischium, forms a thick, fleshy mass, descends almost vertically and terminates 

 about the lower third of the thigh in a rounded tendon which is inserted into the 

 adductor tubercle on the inner condyle of the femur, being connected by a 

 fibrous expansion to the line leading upward from the tubercle to the linea 

 aspera. 



Action. — Adductor of thigh. 



Nerve Supply.- — Obturator and branch of great sciatic. 



Blood Supply. — The femoral and perforating branches of profunda. 



Gluteus maximus. — Description. — (Plate LXV.) — This muscle, which is 

 made up of fasciculi lying parallel with one another, is very coarse in structure. 

 These fasciculi are collected together into large bundles, which are separated by 

 deep cellular intervals. It is a thick and quadrilateral muscle and helps to 

 hold the trunk erect. It is the most superficial muscle in the Gluteal Region. 

 There is a synovial bursa between this muscle and the great trochanter, one 

 between its tendon and the Vastus externus, and often one is situated on the 

 tuberosity of the ischium. 



Origin. — (Plates XLIII-XLV.) — (1) Superior curved line and crest of 

 ilium; (2) posterior surface of lower part of sacrum; (3) side of coccyx; (4) 

 aponeurosis of Erector spina?; (5) great sacro-sciatic ligament and fascia cover- 

 ing Gluteus medius. 



Insertion. — (Plate XLVIII.) — The fibers forming the upper and larger 

 portion of the muscle, together with the superficial fibers of the lower portion, 

 terminate in a thick tendinous lamina, which passes across the great trochanter 

 and is inserted into the fascia lata covering the outer side of the thigh ; the deeper 

 fibers of the lower portion are inserted into the rough line leading from the great 

 trochanter to the linea aspera between the Vastus externus and Adductor mag- 

 nus. 



Action. — Extends, adducts, and rotates the thigh outward. 



Nerve Supply. — Inferior gluteal and small sciatic. 



Blood Supply. — Superior and inferior gluteal. 



Gluteus medius. — Description. — (Plate LXV.) — The posterior border of 

 this muscle lies parallel with the Pyriformis muscle but is separated from it by 

 the gluteal vessels. The posterior one-third of its external surface lies under the 

 Gluteus maximus, its anterior two-thirds under the fascia lata. This is a broad 

 thick, radiating muscle situated on the outer surface of the ilium. A synovial 

 bursa is situated between the tendon of this muscle and the surface of the great 

 trochanter in front of its insertion. 



Origin. — (Plates XLIII-XLV.) — Outer surface of ilium between superior 

 and middle curved lines; (2) crest of ilium; (3) fascia covering outer surface. 



Insertion. — (Plate XLIX.) — Oblique line of great trochanter. 



Action. — Adducts the extended thigh, rotates same and supports body 

 on limb. 



Nerve Supply. — Superior gluteal. 



Blood Supply. — Superior gluteal. 



