MAMMALIA. 



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ribs, that in turn inclose and protect the chest. Third, 

 the lumbar or loin vertebrae, numbering from four to 

 seven. Fourth, the sacral bones, that are anchylosed and 

 form the sacrum ; these generally number from one to 

 nine. Fifth, the caudal or tail vertebrae, that are more 

 movable one upon another than the others, and number 

 from four to forty-six. The tail is a very useful member. 

 In some of the monkeys it serves as a fifth hand ; in the 

 dog it is used to express emotion, and in the horse, ant- 

 eater, and many animals, as a protection from insects. 



Limbs. The mammals generally have four limbs, and 

 from this are termed quadrupeds, though in the whale the 

 hinder pair are not present, or are rudimentary. In Fig. 

 321 we see the fore-limb joined to the body by the shoul- 

 der-blade or scapula, sc, and the clavicle or collar-bone. 

 The first bone of this leg is the humerus, i ; then follow 

 two bones joined together, the radius and ulna, 2, followed 

 in turn by the carpus, 3, or wrist-bone, the metacarpals, 

 that form the upper portion of the hand, and the phalan- 

 ges, 4, or finger and toe bones. The hind-limbs in their 

 parts resemble the fore- ones, and are connected to the 

 body by a number of bones that are joined together and 

 known as the innominate bone, *", and constitute the pelvic 

 arch. The upper bone of the leg is the femur or thigh, 

 5 ; then follow the leg-bones, similar to the ulna and 

 radius, but called the tibia and fibula, 6 ; then the tarsus 

 or ankle-bones, 7, the metatarsus or bones of the foot, 8, 

 and the bones of the toes or phalanges, 9. There are gen- 

 erally five toes, but there are many exceptions, as the 

 horse that walks on the toe-nail of its single toe, the ox 

 on two toes, etc. The limbs are adapted to the habits 

 of the animal. The sloths have long claws for clinging, 

 and the moles powerful digging-claws. In the whales and 

 seals they are paddles. 



Digestion. The jaws of all mammals, except the whale- 

 bone whales and a few others, are provided with teeth 



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