326 



COMPARATIVE ZOOLOGY. 



veloped the primary, secondary, and tertiary feathers of 

 the wing. The hind-limbs are formed for progression — 

 walking, hopping, running, paddling, and also for perch- 

 inc and grasping. The modifications are more numerous 

 and important than those of the bill, wing, or tail. There 

 are twenty bones ordinarily, of which the tibia is the prin- 

 cipal ; but the most characteristic is the tarso-metatarsns, 



which is a fusion of 

 the lower part of the 

 tarsus with the meta- 

 tarsus. The rest of the 

 tarsus is fused with 

 the tibia. The thigh 

 is so short that the 

 knee is never seen out- 

 side of the plumage; 

 the first joint visible 

 is the heel.'" Most 

 Birds have four toes 

 (the external or "lit- 



Fig. 304.— Pi'iiiciiml Parts of a Bird: o, primaries; .-i ,, , ■ i 



&, secondaries ; c, Bpuriou8 wing ; (f,wiug-covert8 ; tie tOe IS alWayS 



, e, teitiaiies; /, thi-oat, or jngulnra; (7, ctiin; A, „„„4.i„„\ . mnnv bflvp 



bill; the meeting-line between the two mandi- Wanting; , mdllj Iiave 



bles is the commissure ; the ridge on the upper ^l^j-gQ tl^g hcMuX OV 

 mandible is called culmen ; that of the lower, _ ' _ ' 



gouys; the space between the base of the upper "big" tOC, being ab- 

 maudible and the eye is the lore : i, forehead ; fc, _^ 



crown; !, scapular feathers ; m, back ; n, meta- Sent; Wlllle the US- 



tarsns, often called tarsus or tarso-metatarsns ; j.'r^i Kf+ f\ r^-n 



o, abdomen; j), rump; g, upper tail-coverts ; r, ll'lCn UaS DUt tWO, aU- 



lower tail-coverts. swcring to the third 



and fourth. The normal number of phalanges, reckoning 

 from the hallux, is 2, 3, 4, 5. The toes always end in 

 claws. 



Birds have neither lips nor teeth, epiglottis nor dia- 

 phragm. The teeth are wanting, because a heavy masti- 

 cating apparatus in the head would be unsuitable for 

 fiight. The beak, crop, and gizzard vary with the food. 

 It is a peculiarity of all Birds, though not confined to 



