SKELETON OF THE WILD DUCK. THE PES. 327 



the way down the shaft. The proximal part of the shaft of 

 the tibio-tarsus bears a roughened ridge with which the fibula 

 is closely connected. The distal end is expanded and rotated 

 outwardly and forms a prominent pulley-like surface which 

 articulates with the tarso-metatarsus. 



The fibula is reduced to the proximal portion only, which 

 is expanded and articulates with a depression behind the 

 external condyle of the femur. The fibula further extends 

 about a third of the way down the shaft of the tibio-tarsus. 

 The patella or knee-cap is a sesamoid bone due to an ossi- 

 fication in the tendon of the extensor muscles of the leg. 



The ankle joint lies between the proximal and distal 

 tarsals which as previously mentioned fuse respectively with 

 the tibia and metatarsus. 



The Pes. The pes includes four digits, and consists of the 

 tarso-metatarsus and the phalanges. The proximal tarsals 

 which are fused with the tibia also really belong to the pes. 



The tarso-metatarsus is a strong straight bone nearly as 

 long as the femur, and is formed by the fusion of the distal 

 tarsals with the second, third and fourth metatarsals. The 

 proximal end of the bone is expanded and bears two facets for 

 articulation with the tibio-tarsus, and near them on the pos- 

 terior surface is a large roughened projection. The lines of 

 junction between the several metatarsals are marked along 

 the shaft by slight ridges. At the distal end of the bone the 

 three metatarsals diverge from one another arid each bears a 

 prominent convex pulley-like surface. The first metatarsal 

 is reduced to the distal end, which tapers to a point proximally, 

 and is attached by ligaments near the distal end of the tarso- 

 metatarsus. 



The digits. Four digits are present, each consisting of a 

 metatarsal (already described) and a certain number of pha- 

 langes, the terminal one being in each case clawed. The first 

 digit or hallux has two phalanges, the second three, the third 

 four, and the fourth five. 



