BIRDS. 



73 



air ; even their bones are hollow, hence very Hght in 

 proportion to their size. The general form of a Bird, 

 and the names of some of the principal external parts, 

 are shown in Figure 102. The skeleton and the names 

 of its principal parts are shown in Figure 103. It is 

 an interesting fact that the form and the skeleton of a 

 bird suggested the right way in which to build a ship 

 in order to combine strength with swiftness. 



Although the body of Birds is covered with feathers, 

 these do not grow from the whole surface, but are ar- 

 ranged in rows and patches, with bare spaces between. 

 Feathers are made up of a hard central portion, or shaft, 



- h 



Fig. 103. — Skeleton of a Bird. 



/i, head; «7'. neck vertebrae; r, wrist; ;"/;, thumb; juc, metacarpus, or hand; //:, 

 phalanges, or lingers; r, radius; ir, ulna; ^, humerus; sc, scapula, or shoulder- 

 blade; cd, corocoid bone; c/, clavicle, or '■ wish bone "; s^, breastbone, or sternum: 

 />, femur, or thigh bone ; /, pelvis; //, fibula and tibia united; /, tibia, or leg; /s, 

 tarsus, or instep; /•s, phalanges, or toes. 



