l88 THE MUSCLES. 



Insertion by tendon and muscle-fibres into a tubercle on the 

 caudal side of the great trochanter at the middle of its distal 

 end, and for a few millimeters into the ridge which continues 

 distad from this tubercle. 



Relations. — Outer surface with the caudofemoralis (Fig. 

 68, s, page 1 17), the superficial fascia, and a few fibres of the 

 cutaneus maximus. Inner surface with the abductor caudle 

 internus, the tenuissimus (Fig. 90, g), the great sciatic nerve 

 (Fig. 163, a), the obturator internus (Fig. 90, r), the gluteus 

 medius (Fig. 90, b'), the gemellus superior, and the pyriformis 

 (Fig. 163, 7). Cranial border with the gluteus medius and 

 the tensor fasciic latae. Caudal border with the caudofemoralis 

 (Fig. 68, s). 



Action. — Abducts the thigh. 



M. gluteus medius (Fig. 90, b). — The gluteus medius is a 

 very large triangular muscle which connects the ilium and the 

 sacrum with the great trochanter (1). 



Origin by fleshy fibres (i) from the superficial sacral fascia; 

 (2) from the lateral surface of the fascia which covers the sur- 

 face of the supraspinous extensor muscles of the tail; (3) from 

 the fascia intervening between it and the tensor fasciiu lataj; 

 (4) by tendon fibres from the dorsal half of the crest of the ilium 

 and its dorsal border, and the dorsal half of the lateral surface 

 craniad of the auricular impression; and (5) from the tips of the 

 transverse processes of the last sacral and the first caudal 

 vertebrae. The fibres converge to a strong internal tendon. 



Insertion into the proximal end of the great trochanter. 



Relations. — Outer surface with the gluteus maximus and 

 tensor fasciae latai, and between these with the strong fascia 

 lying beneath the cutaneus maximus muscle. Inner surface 

 with the gluteus minimus, the pyriformis, and the gemellus 

 superior. Cranial border with the tensor fasciae latae. Caudal 

 border with the gluteus maximus. 



Action. — Abducts the thigh. 



M. pyriformis (Fig. 163, 7). — The pyriformis is a triangu- 

 lar muscle covered by the gluteus maximus and the gluteus 

 medius (Fig. 90, b') and overlying the gemellus superior (Fig. 

 163, 6). 



