728 THE ANATUMl Of THE IlLEEEO GROUSE 



ments are present and thus the formula is ABCDW AnA . This fonnula obtains in 

 Pedioecetes"" and has been found by the writer in Colinus and Gallus. 



In the following discussion of the myology of the hind limb, the terminology of Howeil"^ 

 has been used strictly for the hip and thigh. For the shank and foot, the terminology of 

 Gadow"^ has been followed except in these details: (1) the term "M. flexor profundus s. 

 perforatus" is shortened to "M. flexor profundus"; and (.2) the word "hallucis" is replaced 

 by "digit I". The arrangement of these muscles is illustrated in figure 78. 



In Bonasa M. extensor iliotibialis anterior is the most anterior of the superficial muscles of 

 the thigh. It arises from the anterior part of the raised border of the ilium and passes down 

 over the M. gluteus profundus and the external border of the ilium, forming the anterior edge 

 of the thigh and passing on to the mesial side. Its fascia fuses with those of the M. extensor 

 iliotibialis lateralis and the M. vastus medialis to insert on the crest of the tibia. 



M. extensor iliotibialis lateralis is a large muscle covering the external aspect of the thigh, 

 except the anterior and posterior borders. It arises from the internal margin of the ilium both 

 pre and post acetabular, thus covering the whole postacetabular ridge. It is a very thin 

 muscle with the portion behind the femur being thicker. Its fascia extends over the M. 

 gluteus profundus. Distally, the fascia merges with that of M. vastus lateralis, thus forming 

 an aponeurosis which covers the entire anterior aspect of the knee. Gadow™ considers this 

 muscle as divided into three parts but these are very poorly defined in Bonasa. The insertion 

 passes under the topmost part of the origin of the pars externa of M. gastrocnemius and on 

 to the patella. 



M. gluteus profundus originates from the supero-internal margin of the preacetabular 

 moiety of the ilium and the concave surface of the bone external to it. It lies immediately 

 beneath the aponeurosis of M. extensor iliotibialis lateralis and the proximal portion of M. 

 extensor iliotibialis anterior. The fibers insert by a broad tendon on the head of the femur 

 proximal to the insertion of M. iUacus, pars medius. This muscle is relatively large in Colinus. 



M. iliacus. pars anterior is a small muscle which is only slightly covered by the preceding. 

 It originates along the external border of the acetabular fossa and also from the last rib. The 

 insertion is just distal to the insertion of M. gluteus profundus and is formed by a broad ten- 

 don. In Colinus, the origin is almost entirely fiom the ventral surface of M. gluteus pro- 

 fundus. 



M. iliacus, pars medius originates on the external border of llic ilium about one-half the 

 distance from the acetabulum to the origin of M. iliacus, pars anterior. The insertion is 

 between the insertions of the above muscles. The belly of this muscle is completely covered by 

 M. gluteus profundus. 



M. vastus lateralis underlies M. extensor iliotibialis lateralis. It originates along the antero- 

 external portion of the femur just distal to the insertion of the M. iliacus. pars anterior. Its 

 fascia is, as mentioned above, fused with that of M. extensor iliotibialis lateralis. These pass 

 over the tip of the femur and insert on the patella. In Gallus, the origin overlies the insertion 

 of M. iliacus, pars anterior. In Colinus. the origin is even more proximal, partly covering the 

 insertion of M. iliacus. pars medius and the muscle is divided into two parts. Pars media 

 originates from the proximal one-third of the anterior aspect of the femur. Its fascia fuses 

 distally with that of M. extensor iliotibialis lateralis and inserts on the patella. Pars externa 

 is on the external aspect of the fennir. In Bonasa, pars media is not distinctly separated 

 from pars externa. 



