MUSCULAR SYSTEM OF AVES. 107 



part of the pulley of the gastrocnemius, and expands as it passes 

 along the metatarsus : a thick ligamentous substance is deve- 

 loped in it opposite the joint of the proximal phalanx of the second 

 toe, into the sides of which it is inserted, dividing for that pur- 

 pose, and giving passage to the two other flexor tendons of that 

 toe. The second portion of the present muscle terminates in a 

 tendon situated behind the preceding, which passes through a 

 distinct sheath behind the tarsal joint, expands into a sesamoid 

 fibro-cartilage beneath the corresponding expansion of the previous 

 tendon, which it perforates, and then becomes itself the perforated 

 tendon of the second phalanx of the second toe, in the sides of 

 which it is inserted. The third portion of this muscle ends in a 

 somewhat smaller tendon than the preceding, which forms the 

 second perforatus Jiexor of the third or middle toe. The fourth 

 and most posterior portion soon becomes a distinct muscle ; its 

 fleshy fibres cease on the inner side, one-fourth down the leg, but 

 on the outside they are continued three-fourths down the leg ; its 

 tendon passes through the gastrocnemial pulley behind the ankle- 

 joint, and divides to form a sheath for the Jiexor perforatus of the 

 fourth toe ; it is then joined by the tendon of the peroneus, which 

 passes through a pulley across the external malleolus, and finally 

 becomes the perforated tendon of the first phalanx of the middle 

 or third toe. 



Pectineus (^rectus anticus femoris of Cuvier ^ and Meckel ^). — 

 This is a long, thin, narrow strip of muscle arising from the spine 

 of the pubis, anterior to the acetabulum, and passing straight 

 down the inner side of the thigh ; it degenerates into a small 

 round tendon near the knee, which tendon, fig. 35, 41, traverses 

 a pulley, formed by an oblique perforation in the strong rotular 

 tendon of the extensors of the leg, and thus passing across the 

 knee-joint to the outer side of the leg, finally expands, and is lost 

 in \hQ Jiexor perforatus digitorum last described. It is this muscle 

 which causes the toes to be bent when the knee is bent, as in the 

 act of perching. 



Peroneus longus ^ arises, tendinous from the head of the tibia, 

 and by carneous fibres from the upper half of the anterior margin 

 of the tibia ; these fibres pass obliquely to a marginal tendon, 

 which becomes stronger and of a rounded form where it leaves 

 the muscle. The tendon gives off a broad, thin, aponeurotic 

 sheath to be inserted into the capsule of the tarsal joint ; it is 

 then continued through a synovial pulley on the side of the outer 



* xir. p. 523. 2 XLV1-. th. iii. p. 365. " xi'. vol. iii. pis. 32, 35, 7. 



