. Natural history object lessons : a manual for teachers. mmon domestic animals, the horse, ass, cow, sheep,and pig, as also the rhinoceros, hippopotamus, and tapir,walk on one or more toes. The leg of the horse is a beau-tiful adaptation for the purpose of strength, speed, andspringiness. The upper and lower arms and leg bones cor-respond with those of most other mam-mals, except that the ulna and thetibia are absent, but the bones corre-sponding to our hands and feet arechanged almost out of bones of the knee of the fore legand of the backward-turned knee ofthe hind leg, corr
. Natural history object lessons : a manual for teachers. mmon domestic animals, the horse, ass, cow, sheep,and pig, as also the rhinoceros, hippopotamus, and tapir,walk on one or more toes. The leg of the horse is a beau-tiful adaptation for the purpose of strength, speed, andspringiness. The upper and lower arms and leg bones cor-respond with those of most other mam-mals, except that the ulna and thetibia are absent, but the bones corre-sponding to our hands and feet arechanged almost out of bones of the knee of the fore legand of the backward-turned knee ofthe hind leg, correspond to those ofthe wrist and ankle. If we excepttwo small bones, called splint bones,only one metacarpal and one meta-tarsal bone is present, with three pha-langes at the end of each. The meta-carpal and metatarsal (cannon) bonesare elongated and strengthened, and setupright on the first of the phalanges. The last of thephalanges is partly enclosed by a hoof which correspondstothe finger nail. The rhinoceros and tapir have each three toes; the hippo-. Fig. 100.—Foot ofHorse. ANIMALS AND THEIK USES. 149 potamus, the pig, and the ruminants* generally, have fourtoes. Fashioned on the same principle as that of mammals, theskeleton of birds differs materially in some respects. In thefirst place the bones ofthe limbs instead of be-ing solid, or filled withmarrow, are hollow; andfor these reasons, as sup-ports for the powerfulmuscles they must bestrong, and for the at-tachment of these mus-cles they must be large;while at the same timethey must not be tooheavy, or flight wouldbe impossible. In thesecond place the bonesof the fore limbs aremodified to suit the re-quirements of a winginstead of a hand or bones of the fore-arm are lengthened, theincrease in length bearing relation to the power of flight,while the hand is reduced to a single piece for the supportof the large feathers of the wing. A rudimentary thumband the vestiges of a third finger are, however, present. Int
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