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¬ 
ing 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-metatarsus, 
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. 167 Most 
Birds have four toes 
(the external or “ lit- 
Fig. 304.—Principal Parts of a Bird: a, primaries; . ,, . . 
b, secondaries ; c, spurious wing; d, wing-coverts ; tie toe IS always 
e, tertiaries; /, throat, or jugulum; g , chin; h, wan ti no A . m an v ha VP 
bill; the meeting-line between the two mandi- wanting; , many nave 
bles is the commissure; the ridge on the upper three the hallux or 
mandible is called culmen; that of the lower, ’ J 
gonys; the space between the base of the npper “big” toe, being ab- 
mandible and the eye is the lore; i, forehead; k, & 
crown; l, scapular feathers; m, back; n, meta- Sent J while the US- 
tarsus, often called tarsus or tarso-metatarsus; , . i * K t t 
o, abdomen; p, rump; q, upper tail-coverts; r, ^llCU Las Dllt tWO, an- 
lower taii-coverts. swering 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 
flight. The beak, crop, and gizzard vary with the food.' 1 
It is a peculiarity of all Birds, though not confined to 
