INTRODUCTION. 
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shoulder-blade, the humerus or arm, the cubitus or fore-arm, 
and the hand, with the muscles and quills. The Posterior 
Extremity consists of the femur or thigh, the tibia or leg, 
the tarsus, or what is commonly but erroneously called the 
leg, and the toes, with muscles and other parts. All these 
parts, excepting the bill or anterior part of the jaws, the 
eyes, the tarsi, and the toes, are generally covered with fea- 
thers, attached to the skin. 
Fig. 1. 
The Bill is composed of two mandibles, an upper, 1, and 
a lower, 2, formed of horny substances ensheathing the jaws. 
In the upper mandible are distinguished the base, the ridge, 
of which the outline is named the dorsal line, the sides, the 
edges or margins, and the point. In the lower mandible are 
seen the base, the two crura or branches, their junction or 
the angle, the ridge and its dorsal line, the edges, and the 
point. 
