Mil 



PHYLUM CHORD ATA 



381 



ment shows that the pulley-like distal end of the bone (Fig. 1049, 

 tl.l) consists of the proximal tarsals astragalus and calcaneum 

 tr which at an early period unite with the 



hd_s~-;& tibia and give rise to the compound 



shank-bone of the adult. The fibula 

 (fi.) is very small, much shorter than 

 the tibia, and tapers to a point at its 

 distal end. 



Following the tibio-tarsus is an 

 elongated bone, the tarso-metatarsus 

 (Fig. 1048, ts. mtts.), presenting at its 



foat^$ proximal end a concave surface for the 



^ , tibio-tarsus, and at its distal end three 



distinct pulleys for the articulation of 

 "/* the three forwardly-directed toes. In 



ti.ls 



fth.f. 



third, and mtl.4, 



1, proximal tarsal 



cartilage. (From 



ph.* 



-ts.mlls 



FIG. 1049. Columba livia. Part of left foot of an 

 unhatched embryo (magnified). The cartilage is 

 dotted. mtl. 2, second, mtl. 3, 

 fourth metatarsal ; ti. tibia ; U. 

 cartilage ; tl. 2, distal tarsal 

 Parker's Zootomy.) 



the young Bird the proximal end of 

 this bone is a separate cartilage (Fig. 

 1049, tl.2), representing the distal 

 tarsals, and followed by three distinct 

 metatarsals, belonging respectively to 

 the second, third, and fourth digits. 

 Thus the ankle-joint of the bird is a 

 mesotarsal joint, occurring, as in the 

 Lizard, between the proximal and 

 distal tarsals, and not, as in Mammals 

 (q.v.), between the tibia and the proxi- 

 mal tarsals. To the inner or pre-axial 

 side of the tarso-metatarsus, near its 

 distal end, is attached by fibrous tissue a small irregular bone, the 

 first metatarsal (Fig. 1048, mtts.^1). The digits have the same 



FIG. 1048. Columba livia. 



Bones of the left hind-limb. 

 cn.pr. cneinlal process ;fe. femur ; 

 ft. fibula ; hd. head of femur ; 

 mtts. J, first metatarsal ; pat. 

 patella ; ph.l, phalanges of first 

 digit ; ph.4, phalanges of fourth 

 digit ; ti. ts. tibio-tarsus ; ts. 

 mtts. tarso-metatarsus ; tr. tro- 

 chanter. 



