314 COMPARATIVE ZOOLOGY. 
ted for flight. They ordinarily consist of nine separate 
bones, and from the hand, fore-arm, and humerus are de- 
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: 
characteristicis the tar- 
so-metatarsus, which 
is a fusion of the low- 
er part of the tarsns 
with the metatarsus. 
The thigh is so short, 
the knee is never seen 
outside of the plum- 
age; the first joint 
visible is the heel.” 
Most Birds have four 
h g f edeb a toes (the external or 
ile atone ecm ieieclarann ota rir 
e, tertiaries; f, throat, or jugulum; g, chin; h, wanting) ; many have 
bill; the meeting line between the two mandi- 
bles is the commissure; the ridge on the upper three, the Aallua. or 
mandible is called culmen; that of the lower, Z 2 
gonys; the space between the base of the upper e big” toe, being ab- 
mandible and the eye is the lore; 7, forehead; &, igs o Tee 
crown; 1, scapular feathers; m, back; n, meta- sent; while the Ostrich 
tarsus, often called tarsus or tarso-metatarsus ; 0, t A 
abdomen; p, rump; qg, upper tail-coverts ; 7, low- has but tw 0, answel 
eee. ing 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 mas- 
ticating apparatus in the head would be unsuitable for 
flight. The beak, crop, and gizzard vary with the food. 
The sole organs of prehension are the beak and legs. The 
