328 



Fossa iliaca 



Muscles of the Leg. 



Os sacrum 



M. piriformis 



coccygis 



M. coccygeus 



Faoics syniphyseos 

 ossis pubis 



UKamentum sacrotuberosuin 



('aiuilis obturatorius 



FcTiiiir -_x 



M. obturator internus 



373. Muscles of the true pelvis on the right side, 



viewed from witliiii. 



M. obturator iiiteruus (sec also Figs. 374 and 385). Forni: flat, triangular. Position: 

 in the small or true pelvis, on its lateral wall and close behind the hip-joint. Origin: medial 

 surface of the os coxae and of the memhrana obturatoria. Insertion: tlii^ tibt,n's converge to 

 the incisura ischiadica minor; tli(>r(> they Ijend lateralward (bursa m. obturutoris intend see 

 Fig. 380) ;it a right angle and becoming tendinous pass between the two mm. gemeUi to tbe fossa 

 trochanteri<-a femoris. Action: it rotates the thigh outward. Innervation: n. til)ialis. 



M. coccygeus (see also Figs. 374, 670 and 671). Form: quadrangular, thin. Po- 

 sition: on the anterior surface of tlie lig. sacrospinosum, fornn'ng with it a common mass of 

 variable composition (see p. 194); it projects beyond it, esi)ecially l)elow. Origin: spina 

 ischiadica. Insertion: lateral edge of lower sacral and upper coccygeal vertebrae. Inner- 

 vation: branches of the plexus ]iii(liMidus. 



