MAMMALIA. 633 



(709.) The MAMMALIA, as we might be prepared to antici- 

 pate from their importance, are extensively distributed. The 

 generality of them are terrestrial in their habits, either browsing 

 the herbage from the ground, or, if of carnivorous propensities, 

 leading a life of rapine, by carrying on a blood-thirsty warfare 

 against animals inferior to themselves in strength or ferocity. 

 Many inhabit the trees ; some burrow beneath the surface of 

 the soil ; a few can raise themselves into the air and flit about 

 in search of insect prey; the Otter and the Seal persecute the 

 fishes even in their own element ; and the gigantic Whales, wal- 

 lowing upon the surface of the sea, " tempest the ocean" in their 

 fury. 



(710.) With habits so diverse, we may well expect correspond- 

 ing diversity in their forms, or in the structure of their limbs ; and, 

 in fact, did we not compress our description of these particulars 

 into reasonable limits, we might easily test the perseverance of the 

 most patient reader in following us through the mass of details 

 connected with this part of our subject. We shall, therefore, 

 commencing as we have hitherto done, with the osteology of the 

 class, first describe, in general terms, the characters of a Mam- 

 miferous skeleton ; and then, as we arrange the Mammalia under 

 the various orders into which they have been distributed, speak of 

 the most important aberrations from the given type. 



(711.) The vertebral column of all Mammals, with the remark- 

 able exception of the Cetacea, is divisible into the same regions as 

 in the human skeleton, viz. the cervical, dorsal, lumbar, sacral, and 

 coccygeal or caudal portions. 



The cervical vertebrae are invariably seven in number. The 

 Sloth (Bradypus tridactylus) was, until recently, regarded as 

 forming a solitary exception, it having been supposed to possess 

 nine cervical vertebrae ; the researches of Professor Bell, however, 

 show, that even this animal conforms to the general law. The dis- 

 tinguished naturalist referred to* has demonstrated, " that the pos- 

 terior two of these vertebrae have attached to them the rudiments 

 of two pairs of ribs, in the form of small elongated bones articulated 

 to their transverse processes ; they must, therefore, be considered 

 as truly dorsal vertebrae, modified into a cervical form and function 

 suited to the peculiar wants of the animal/ 1 Professor Bell fur- 

 ther observes, that " the object of the increased number of ver- 



* Cyclop, of Anat. and Phys. art. EULNTATA. 



