Page:First course in biology (IA firstcourseinbio00bailrich).pdf/390

 The pigeon has toes, the hind toe having joints; of the three front toes, the inner has joints (count the claw as one joint), the middle has joints, and the outer toe has joints (Fig. 285). Is the thigh of a bird bare or feathered? The shin? The ankle? Where is the ankle joint of a bird? Do you see the remains of another bone (the splint bone, or fibula) on the shin bone of the shank? (Fig. 285 or 286.) Why would several joints in the ankle be a disadvantage to a bird?

Rh, vertebræ; Cl, clavicle; Co, coracoid; Sc, scapula; St, sternum; H, humerus; R, radius; U, ulna; P, thumb; Fe, femur; T, tibia. See Fig. 394.

Questions: Which is the stiffest portion of the vertebral column? How are the ribs braced against each other? Which is longer, thigh bone or shin? Compare shoulder blade with man's (Fig. 399). Which is the extra shoulder bone? Compare tail vertebræ with those of extinct bird, Fig. 290.