MUSCLES OF TEE POSTEBIOR LIMBS. 293 



of the sacrum to the inferior extremity of the femur, following the direction 

 of the ischiatic border of the ilium, into which it is inserted. The tendon 

 to which it owes its penniform shape is inflected outwards, behind the supra- 

 cotyloid crest or sciatic ridge, joins the gemelli, and terminates in the 

 bottom of the trochanterian fossa. 



Belations. — In its intrapelvic portion, this muscle responds: outwards 



COCCYGEAL AND DEEP linSCLES SUEEOUNDING THE COXO-FEMOKAL AETIOULATION. 



1, Superior sacro-coccygeus ; 2, Lateral sacro-coccygeus ; 3, Inferior sacro-coccygeus ; 

 4, /scliio-coccygeus ; 5, Small gluteus ; 6, Anterior gracilis ; 7, Tendon of the 

 internal obturator; 8, 8, Gemelli of the pelvis; 9, Accessory fasciculus of the 

 gemelli; 10, Quadratus cruralis; 11, Sacro-sciatic ligament; 12, Great sciatic 

 notch ; 13, Superior ilio-sacral ligament ; 14, Inferior ilio-sacral ligament. 



and downwards, to the ilium, pubis, ischium, and external obturator ; inwards 

 and upwards, to the peritoneum, important vessels and nerves, and to a 

 fibrous lamina that separates it from the bladder. In its extra-pelvic 

 portion, it is in relation with : behind, the middle gluteal musclp and the 

 sciatic nerves ; in front, with the gemelli. A synovial sheath facilitates the 

 gliding of its tendon in the groove in which it turns. 



Action. — It is a rotator of the thigh outwards, and, contrary to the 

 opinion of the majority of authors, we believe it to produce abduction rather 

 than adduction, if at any time its position allows it to execute either of these 

 two movements. 



9. Gemelli of the Pelvis (Fig. 131, 8, 8, 9). 

 Synonyms. — Ischio-troehanterius — Girard. (^Gemini — PercivaU. Bifemoro-calcanem 

 — Leyh.) 



The two small muscles which receive this name are far from presenting 

 the same disposition in every subject; but we will describe that which 

 appears to be the most frequent. Two little elongated muscular fasciculi 

 are usually found, one above, the other below the tendon common to the two 

 portions of the internal obturator. These two fasciculi (Fig. 131, 8, 8), 

 arise from the external border of the ischium, follow the direction of the 

 above-mentioned tendon, and are inserted into it by the external extremities 

 of their fibres, exactly representing the gemelli of Man. But there is also 

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