144 ANATOMY IN A NUTSHELL 



brim, reaching from the upper part of the great sacro-sciatie foramen above and 

 behind to the thyroid foramen below and in front. It also arises from the inner 

 surface of obturator membrane except at its posterior part, from the tendinous 

 arch which completes the canal for the passage of the obturator vessels and 

 nerve, and to a slight extent from the obturator layer of the pelvic fascia which 

 covers it. 



Insertion. — (Plate XLIX.) — Into the fore part of the inner surface of 

 great trochanter in front of obturator externus, together with the Gemelli. 



Action.— Rotates and abducts thigh. 



Nerve Supply. — Fifth lumbar, first and second sacral. 



Bi.< >( id Supply.— Sciatic 



LESSON XXXVIII. 



Gemellus superior. — Description. — (Plate LXY.) — This muscle is not 

 always present. It is an aid to the Obturator internus. It has a common tendon 

 with the Obturator internus. It is smaller than the Gemellus inferior. 



Origin. — (Plate XLIY.) — Outer surface of spine of ischium and blends 

 with tendon of Obturator internus. 



I nsertion. — (Plate XLIX.)— Inner surface of great trochanter. 



A.< tion. — Rotates the extended thigh, abducts the flexed thigh. 



Nerve Supply. — Fifth lumbar, first and second sacral. 



Blood Supply. — Sciatic and external circumflex. 



Gemellus inferior. — Description. — (Plate LXY.) — This muscle is larger 

 than the Gemellus superior and like that muscle is an aid to the Obturator in- 

 terims. 



Origin. — (Plate LXIII.) — Upper part of tuberosity of ischium and blends 

 with tendon of ( >bturator internus below. 



Insertion. — (Plate XLIX.) — Inner surface of great trochanter. 



Action. Rotates extended thigh, abducts flexed thigh. 



\'u;\ e Supply.— Fourth and fifth lumbar and first sacral. 



Blood Supply. — Sciatic and external circumflex. 



Quadrat us femoris.— 1 )ks<ription. — (Plate XLY.) — This muscle is sit- 

 uated between the upper margin of the Adductor magnus and the Gemellus in- 

 ferior. It is flat and quadrilateral. The terminal branches of the internal cir- 

 cumflex vessels lie between the Adductor magnus and this muscle. 



Origin. (Plate XLIII.) — Upper part of external lip of tuberosity of 

 ischium. 



Insertion. (Plate XLVIII.) — Quadrate line of femur, upper part. 



A' tion.- Rotates thigh outward. 



Nerve Supply. Las1 lumbar and first sacral. 



Blood Si pply. Sciatic and internal circumflex. 



Obturator externus. Description.- (Plate LXXI.) — The deep branches 

 of the obturator nerve perforate tins muscle while the superficial ones pass above 

 it. The obturator vessels lie between this muscle and the obturator membrane. 



