THE ANATOMY OF THE RUFFED GROUSE 735 



metatarsus is flexed on the tibia by M. tibialis anticus and extended by M. gastrocnemius and 

 M. peroneus superficialis. M. plantaris is a weak extensor of the tarso-metatarsus. M. 

 peroneus brevis abducts the tarso-metatarsus. The fibula and tibia are drawn together by M. 

 popliteus. 



M. extensor digitorum communis is assisted in the extension of the fore toes by M. extensor 

 brevis digiti II and M. extensor brevis digiti IV. Digit 1 (hind toe) is extended by M. exten- 

 sor brevis digiti I. The muscles for the flexion of the toes are numerous. M. flexor perforatus 

 has a separate tendon to each of the fore toes. M. ambiens acts on digit II through the connec- 

 tion of its tendon with M. flexor perforatus digiti II. M. flexor perforans et perforatus digiti 

 II and M. flexor perforans et perforatus digiti III act to flex the more distal phalanges. M. 

 peroneus superficialis acts on digit III since its tendon attaches to the tendon of M. flexor 

 perforans et perforatus digiti III. In addition. M. flexor profundus has a branch to each of 

 the fore toes. Digit I is flexed by M. flexor longus digiti I. There is a M. flexor brevis for 

 digit I. Digit II has a small abductor and adductor and digit IV has an abductor. The 

 presence of a vinculum between M. flexor profundus and M. flexor longus digiti 1 and also 

 between M. flexor perforatus digiti III and M. flexor perforans et perforatus digiti 111 tends 

 to result in unity of action for the toes. 



Wing. The following are brief descriptions of the important muscles* of the wing (figure 

 79.) 



r coa eejKM POST 



' JUPeACOA 



FIGURE 79'^. WING MUSCULATURE. LATERAL VIEW OF DEEP MUSCLES (x 0.43) 



M. rhoinboideus superficialis originates on the last cervical vertebra and along the crests 

 of the first three thoracic vertebrae. The muscle extends as a wide band to the scapula and 

 also extends forward to insert on the dorsal part of the clavicle. 



M. rhomboideus profundus underlies M. rhomboideus superficialis. Its origin is from the 

 neural crests of the last cervical vertebra and all five thoracic vertebrae. The insertion is on 

 the dorsal border of the scajuila just under that of M. rhomboideus superficialis. 



M. pectoralis superficialis is divided into three parts. M. pectoralis thoracicus originates 

 along the ventral part of the sternum, the niembrana sterno-coraco-clavicularis and clavicle, 

 and inserts on the lateral crest of the humerus. This is the great flexor of the wing. M. pec- 

 toralis propatagialis is a poorly defined slip which has a small extension to the propatagial 

 ligament. M. pectoralis abdominis extends just under the skin from the pubis to the lateral 



» Tcrn.in..loev acc.nlinp In H.mpll. A. B. 1'". 

 A For explanation of alibrpviations. see p. 740. 



