THE MUSCLES OF THE LOWER EXTREMITY. 185 



It may be as well to observe that the point of insertion 

 of this muscle upon the shaft of the femur is some little 

 distance below that of the glutens minimus ; the vastus 

 externus of the extensor femoris passes up between 

 these two muscles, and the femoro-caudal itself overlies 

 the adductor muscles which pass down between it and 

 the pelvis ; so that its insertion may also be said to be 

 on a narrow vertical line between the insertions of the 

 vastus externus and the adductors. 1 



In my memoir upon Geococcyx I said that in that 

 genus " The femoro-caudal muscle and the accessory 

 femoro-caudal are both present and fully developed. 



" The femoro-caudal (Fig. 64 bis) arises, tendinous, 

 from the lower posterior border of the pygostyle. It 

 soon becomes fleshy, and as a narrow, muscular ribbon 

 passes through the tissues overlying the lateral group of 

 caudal muscles proper. Opposite the posterior border 

 of the pelvis it expands to form a prettily-shaped and 

 compressed spindle, closely covering the obturator ex- 

 ternus muscle and the side of that bone. As it nears 

 the femur it again contracts, receives the fibres of its 

 accessory head, and is finally inserted upon the femoral 

 shaft, at the posterior aspect of its proximal third. 



1 Many birds have an accessory femoro-caudal ; it is absent in the 

 Raven. It is described by Garrod as " an accessory head, arising 

 from, the upper three-fourths of the postacetabular ridge, and from 

 the ridge which forms the lower margin of the origin of the ob- 

 turator externus, joins the tendon of insertion of this muscle, and 

 is also partly inserted into the linea aspera, between it and the 

 head of the femur. It is thin, muscular, and broad, covering the 

 obturator externus superficially, and is partially intersected by a 

 fibrous sheet where it crosses its anterior border. The sciatic artery 

 and nerve cross it superficially ; and the nerve to the semimem- 

 branosus is deep of it, whilst that to the semitendinosus is superficial 

 in some cases ; the biceps completely covers it " (Coll. Scientific 

 Memoirs, p. 191). 



