THE ANATOMY OF THE RUFFED GROUSE 731 



cruris medialis and M. flexor cruris lateralis, passes internal to the pars interna of M. gastroc- 

 nemius and passes over M. plantaris and then inserts on the tibia, just distal to the mesial 

 condyle. In Colinus, M. flexor cruris medialis is relatively small. 



M. caudofemoralis inserts along the external aspect of the shaft of the femur below M. 

 vastus lateralis. As a thin curved band of parallel fibers, it passes over the ischium from its 

 origin on the caudal vertebrae. 



M. flexor iliofemoralis arises beneath the rim of the postacetabular portion of the ilium, 

 posterior to the ischiadic foramen. It passes obliquely to insert with M. caudofemoralis. In 

 Gallus M. flexor iliofemoralis differs greatly. It has two bellies, connected by a fascia. The 

 medial belly inserts on the posterior border of the obturator foramen. 



M. obturator arises from the entire ventral surface of the ilium. It is broad at the posterior 

 part and then narrows as it passes anteriorly. Its fibers join to form the tendon which passes 

 through the obturator foramen and inserts on the outer aspect of the femur opposite to the 

 insertion of M. extensor iliotibialis lateralis. In Gallus and Colinus, this muscle is large and 

 extends up onto the ventral surface of the ilium. 



Mm. accessorii m. obturatus. This group of muscles has only one small representative in 

 Bonasa and Gallus. It stretches from the fossa between the obturator foramen and the aceta- 

 bular foramen to the trochanter of the femur and inserts with the previous muscle. 



M. adductor superficialis originates along the pubis just posterior to the obturator foramen. 

 It passes as a band of fibers parallel to the femur to insert on the femur, posterior to the 

 insertion of M. femorocruralis and also in the fossa between the condyles. 



M. adductor profundus lies immediately mesial to the M. adductor superficialis. Its pubic 

 portion is partly formed from an aponeurosis which is attached to the pars externa. The 

 insertion is along the distal two-thirds of the femur, but mainly in the condylar fossa. 



M. gastrocnemius is the large muscle covering most of the posterior and internal aspects 

 of the lower leg. It is composed of three parts. The pars externa has its origin on the outer 

 condyle of the femur. The outer part of the tendinous loop for the M. extensor iliofibularis 

 also originates at this point. This is proximal to the insertion of M. extensor iliotibialis 

 lateralis and M. vastus lateralis. This part is fairly long and thin and is distinct from the two 

 other parts. The pars media arises from the inner surface of the inner condyle of the femur. 

 It is small and soon fuses with the rest of the muscle. The tendon formed by M. flexor cruris 

 lateralis and M. flexor cruris medialis fuses with it and ])asses through to insert on the internal 

 aspect of the tibia. M. femorocruralis is not connected with the pars media in Bonasa as it is 

 in Colinus. The pars interna takes its origin from the inner rim of the tibial summit and 

 the fascia of M. extensor iliotibialis anterior. This is the largest division of the muscle. The 

 tendon (tendo Achillis) is formed from the tendons of the pars externa and the pars interna 

 (the tendon of pars media has fused more proximally). It passes over the tarsal joint in a 

 groove of the tibial cartilage and inserts on the larso-nietatarsus just distal of the proximal 

 head. The tendon is perforate for the other tendons which pass over the back of the joint, 

 thus inserting in two "parts. Part of the tendon continues along the ventral surface of the 

 tarso-metatarsus and inserts in the region of the accessory metatarsal. 



M. plantaris is a small muscle lying just under the pars interna of M. gastrocnemius and 

 originating on the internal crest of the tibia. Its tendon inserts on the tibial cartilage. The 

 fascia of M. flexor cruris medialis passes over (mesiad) its belly to insert on the inner edge 

 of the tibia. 



