COMPARATIVE ZOOLOGY. 
326 
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. 187 Most 
Birds have four toes 
(the external or “ lit¬ 
tle” toe is always 
wanting); many have 
three, the hallux , or 
“big” toe, being ab¬ 
sent ; while the Os¬ 
trich has but two, an¬ 
swering to the third 
o f « 
Fig. 304.—Principal Parts of a Bird: a , primaries; 
6, secondaries; c, spurious wing; d, wing-coverts; 
e, tertiaries; /, throat, or jugulum ; g, chin; h, 
bill; the meeting-line between the two mandi¬ 
bles is the commissure; the ridge on the upper 
mandible is called culmen; that of the lower, 
gonys; the space between the base of the upper 
mandible and the eye is the lore; i, forehead; k, 
crown; l, scapular feathers; m, back; n, meta¬ 
tarsus, often called tarsus or tarso-metatarsus; 
o, abdomen; p, rump; q, upper tail-coverts; r, 
lower tail-coverts. 
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. 
It is a peculiarity of all Birds, though not confined to 
