. Principles of economic zoo?logy. Zoology, Economic. AVES 263 tilian habit of shedding theirs in great flakes, with feathers ;' General Structure.—The skull (Fig. 214) is thin; the bill or horny beak varies much according to its use; and there is, as in reptiles, only one occipital condyle. The neck is long and flex- ible. In different kinds of birds, the number of neck vertebrae varies from eight to twenty-four. The wings are adapted for flight in our birds. While the ostrich cannot fly, its rudimentary wings are compensated for by its very strong legs, which are adapted for ra
. Principles of economic zoo?logy. Zoology, Economic. AVES 263 tilian habit of shedding theirs in great flakes, with feathers ;' General Structure.—The skull (Fig. 214) is thin; the bill or horny beak varies much according to its use; and there is, as in reptiles, only one occipital condyle. The neck is long and flex- ible. In different kinds of birds, the number of neck vertebrae varies from eight to twenty-four. The wings are adapted for flight in our birds. While the ostrich cannot fly, its rudimentary wings are compensated for by its very strong legs, which are adapted for rapid running. No other animal has wings of the same structure as a bird's. The characteristic structure of the wing-bones is the hand. It is comparable with the human Fig. 214.—Skull of parrot: 22, Premaxillary bone ensheathed in horn; 15, nasal bones; v, mandible, the end sheathed with horn; I, malosquamosal zygomatic style or maxillojugal bar; g, postfrontal bone; o, lacrimal bone; n, nostril, showing also the articulation of the nasopremaxillary bone; e, quadrate bone; to, orbit; 1, occipital bone. (After Owen.) The legs and feet (Fig. 215) of birds are adapted for running, scratching, swimming, or perching. Note the position of the thigh (femur) on the side of a bird. Do you see any advantage of such a position? Distally the femur or thigh is joined to the tibiotarsus and the fibula, which is found partially united with the tibiotarsus. The proximal row of tarsal bones unites with the distal end of the tibia, hence the name tibiotarsus or "drum- stick" in the chicken. The distal row of tarsal bones unites with the metatarsal bones to form the tarsometatarsus or simply the tarsus, which bears the usually four-clawed toes. One toe is generally directed backward and three forward. Where is the knee in the bird? The ankle? Do you see any 1 Baskett, " Story of the Birds," p. Please note that these images are extracted from scanned page images t
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