THE ANATOMY OF THE RUFFED GKOiSE 733 



and M. flexor perforatus digili III. '\Uc U-iidon passes through the tibial cartilage to the 

 basal phalanx of digit IV. The flexion of the second and third phalanges of digit IV is 

 accomplished by tendons which have split off^ from the tendon of M. flexor perforatus digiti 

 IV after it has passed the basal phalanx. 



M. flexor perforatus digiti III is divided into two parts. The smaller originates from the 

 strong tendon connected with that of M. ambiens and is thus connected with M. flexor per- 

 foratus digiti IV. The larger division originates from the tendon in the intercondylar region. 

 The tendons of the two divisions join after passing through the tibial cartilage and then 

 receive the tendon of M. peroneus superficialis. A vinculum joins the tendons of this muscle 

 and M. flexor perforans et perforatus digiti III just proximal to the toes. The insertion is on 

 the basal phalanx only. Gadow'" mentions great variation in this muscle. In Gallus, there 

 is no division into two parts. In Colinus, this muscle is divided into two distinct parts and is 

 not fused with M. flexor perforatus digiti IV. 



M. flexor perforatus digiti II may be considered to originate as the tendon from the inter- 

 condylar region. This muscle is most mesial and separates from the main body to form its 

 tendon. This passes through the tibial cartilage and extends to the basal phalanx of digit II. 

 In Gallus it is separated from the main body only a short distance before it forms its tendon. 



The flexion of the second phalanx of digits II and III is performed by the M. flexor per- 

 forans et perforatus group. The tendon passes through the perforation of the tendon of M. 

 flexor perforatus at its insertion on the basal plialanx and inserts on the second phalanx. This 

 insertion is perforated for the passage of the tendon of M. flexor profundus. 



M. flexor perforans et perforatus digit II is a superficial muscle arising from tlie fascia 

 (immediately proximal to the external part of the loop for M. extensor iliofibularis) covering 

 the lateral condyle of the femur, anterior to the pars externa of M. gastrocnemius. It is a 

 small, tliin, but wide muscle which soon forms its tendon. This passes through the tibial 

 cartilage to insert on digit II. In Gallus, it differs greatly. Its middle portion (which is 

 mainly fascia in Bonasa) has disappeared, leaving an anterior and a posterior head. The 

 anterior division, however, has a small belly, distal to the main part of M. flexor perforans et 

 perforatus digiti II, which is attached to the posterior head by a slender strip of fascia. The 

 two tendons fuse at once. 



M. flexor perforans et perforatus digiti III is a large muscle lying immediately anterior to 

 and partly under the above muscle. It arises, in part, from the fibula but mainly from the 

 fascia, immediately anterior to the origin of M. flexor perforans et perforatus digiti II. Its 

 tendon passes through the tibial cartilage to its insertion. In Gallus, this muscle is relatively 

 short. 



M. flexor profundus is the deepest of all the muscles at the back of the tibia. It arises along 

 the proximal two-thirds of the tibia and along the fibula. The origin is not double as Hud- 

 son^" found it in Pedioecetes. The tendon passes over the tarsal joint, deepest in the tibial 

 cartilage, and along the under surface of the tarso-metatarsus. It is connected by the vinculum 

 with the tendon of M. flexor longus digiti I. Beyond this point it trifurcates, one tendon going 

 to each of the three anterior toes to insert on the penultimate and ungual phalanx. 



M. flexor longus digiti I is a small muscle arising from the posterior aspect of the fennir 

 between the condyles, just distal to the origin of M. flexor perforatus digiti IV. and mesial to 

 the tendon of M. extensor ilioflexorius. It soon forms its tendon which passes down through 

 the tibial cartilage and then mesially across the tarso-metatarsus to digit I. It passes external 



