378 MUSCLES OF THE OS FEMORIS. 



trochanter major,, for some way downwards, as far as the origin 

 of the short head of the biceps flexor cruris — and also into the 

 fascia femoris. 



Use. To extend the thigh, by pulling it directly backwards, 

 and a little outwards. 



Second layer, 



Gluteus Medius, 



Arises, fleshy, from the anterior superior spinous process of 

 the OS ilium, and from all the outer edge of the spine of the 

 ilium ; except its posterior part, where it arises from the dorsum 

 of that bone. 



Inserted, by a broad tendon, into the outer and upper mar- 

 gin of the trochanter major. 



Use. To draw the thigh bone outwards, and a little back- 

 wards : to roll the thigh bone outwards, especially when it is 

 bended. 



N. B. The anterior and upper part of this muscle is covered 

 by a tendinous membrane, from which a number of its fleshy 

 fibres arise, and which joins with the broad tendons of the 

 gluteus maximus, tensor vaginae femoris, and latissimus dorsi. 



Third lavt.n' consists of four muscles. 



1. Gluteus Minimus. 



Arises, fleshy, from a ridge that is continued from the superior 

 anterior spinous process of the os ilium, and from the middle 

 of the dorsum of that bone, as far back as its great niche. 



Inserted, by a strong tendon, into the fore and upper part of 

 the trochanter major. 



Use. To assist the former in pulling the thigh outwards and 

 backwards, and in rolling it. 



2. Pyriformis. 



Arises, within the pelvis, by three tendinous and fleshy ori- 

 gins, from the second, third, and fourth pieces of the os sacrum : 

 from thence growing gradually narrower, it passes out of the 



