732 THE ANAT()M\ Of THE liUEEEJ) GIIUVSE 



M. peroneus superficialis is a broad tliin muscle which covers the anterior aspect of the 

 tibia. Its origin is on the cnemial crest of the tibia. The tendon passes along the extero- 

 lateral aspect and divides just proximal to the tibial condyles. The larger branch passes 

 over to the posterior side and inserts on the under surface of the tibial cartilage just external 

 to the insertion of the tendon of M. plantaris. The other branch continues along the lateral 

 aspect, passing under a tendinous bridge, past the joint and inserts on the tendon of M. flexor 

 perforatus digiti III. In Gallus, there is no bridge. Coliniis has a slight one. 



M. peroneus profundus originates along the anterior aspect of the fibula and the lateral 

 [lart of the tibia. It is attached to these bones for its entire length. The tendon is formed 

 about a centimeter above the joint and passes under a tendinous bridge and over the lateral 

 side of the joint and inserts on the summit of the larso-metatarsus. The tendon widens out 

 into a strap-like band as it passes over the joint. 



M. pophteus is situated on the posterior side of the fibula and tibia just below the heads. 

 It is the most deeply placed muscle. The origin is on the fibula and the insertion is on the 

 adjacent area of the tibia. 



The origin of M. tibialis anticus is underneath that of M. peroneus superficialis from the 

 pro- and ecto-cnemial crests of the tibia. There is no femoral head in Bonasa. The tendon 

 passes under an oblique fibro-cartilage bridge and over the anterior surface of the tibial con- 

 dyles, to insert on a tubercle just below the head of the tarso-metalarsus. The tendon becomes 

 wider and cartilaginous as it passes over the tibial cartilage. 



M. extensor digitorum communis originates from the procnemial crest of the tibia, mesiad 

 to the M. tibialis anticus, and passes along the anterior aspect of the tibia. The external 

 edge is flattened out and closely appressed to the tibia. The tendon passes under a bony 

 bridge just proximal to the tibial condyles. Just above and mesial to the tubercle for the 

 insertion of the M. tibialis anticus on the tarso-metatarsus the tendon passes through a 

 fibrous bridge. About midway along the anterior surface of the tarso-metatarsus. the tendon 

 divides into two branches, the external one soon bifurcating again. The internal branch 

 divides at the base of digit II, one half going to digit II and the other half inserting on the 

 liasal phalanx of digit I. Each branch passes to the dorsal aspect of the toe and divides 

 to form the tendons for each phalanx. 



M. flexor perforatus is the principal flexor of the toes. In Bonasa, as in most birds, it is 

 divided inlo lliice |)arls whose bellies are connected together but have distinct tendons. The 

 origin is by a strong tendon from llie intercondylar fossa, a tendinous slip from the external 

 portion of the sling of M. extensor iliofibularis, and a strong tendon from the ectocnemial 

 crest which receives the tendon of M. ambiens. The insertion is on the phalanges and is per- 

 forated for the passage of the other tendons to the phalanges. 



In Coliniis. this muscle is split into its components quite distinctly. The origin of each 

 part is separate from the others. M. perforatus digiti IV has two places of origin, one 

 passing on the cNtcrna! and one passing on the internal side of the tendon of M. extensor 

 iiiofdiularis. 



M. flexor perforatus digiti IV is the most superficial of the group and is triangular and 

 thin. The origin is from the intercondylar region (mesial to the tendon of M. extensor 

 iliofibularis I and. also, from a fascia which extends up onto the external |)arl of the slinu 

 for the tendon of M. extensor iliofibularis. Thus this origin is lateral to that tendon. The 

 intercondylar origin is independent of the tendinous origin of M. flexor perforatus digiti II 



