MUSCLES OF THE HIND LIMB 93 



Femorocaudal? — This is another of the variable muscles 

 of the thigh. Typically the muscle is two-headed, one head 

 arising from the transverse processes of the caudal vertebrae, 

 the other (termed by Gareod accessory femorocaudal) from 

 the ilium. The two are inserted together upon the flexor 

 side of the femur, as a rule by a longish tendon. 



The variations culminate in the entire absence of the 

 muscle, which occurs in Gliunga Burmeisteri and Leptoptilus. 

 In some species — for example, in most Passeres and picarian 

 birds — the caudal portion is alone present. In others — e.g. in 

 Serpentarius, Otis, Phoenicopterus, the iliac portion is alone 

 present. 



Biceps Femoris.^ — This muscle is covered externally by 

 the glutsBus maximus where this is present ; otherwise it is 

 the most superficial of the flexors of the leg. It arises from 

 the postacetabular region of the ilium, and ends in a strong, 

 generally round, tendon, which passes through a sling of 

 tendon which is derived from the femur independently, and 

 from the same bone in common with one of the heads of the 

 gastrocnemius, to be inserted on to the fibula. The principal 

 variations of the muscle concern its more or less extensive 

 origin. It has never been known to be absent. In Cory- 

 thaix Gadow states that it is double. In the ostrich and in 

 the ducks and swans there is the usual sling, but before 

 entering the sling the biceps gives off a branch, which joins 

 one of the heads of the gastrocnemius. In Fregata and in 

 some swifts quite exceptionally the sling is totally absent, 

 but the muscle has the usual insertion. In certain auks the 

 muscle gives off, before entering the biceps sling, a branch 

 to the thigh superficially. In Podica senegalensis the 

 muscle divides into three branches. The first of these has 

 a considerable superficial attachment to the outside of the 

 leg ; the second is attached to the fibula below the attach- 

 ment of the third insertion, which is the normal one, through 

 a sling. In Heliornis only the first and third of these are 

 present. 



> ' Caud-ilio-femoralis ' (Gadow). " ' Ilio-fibularis ' (Gadow). 



