VERTEBRATA. 



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Division I. VERTEBRATA. 



This division of the Animal Kingdom, including the five im- 

 portant classes of Mammalia, Birds, Reptiles, Amphibia, and Fishes, 

 is denominated Vertebrata, all the species having a vertebrated 

 column, called the backbone, constituting the basis of the entire skeleton. They arc distinguished 

 for having the nervous matter, the instrument of all intelligence, concentrated in a single mass, 

 which ma}-, however, be considered as consisting of two parts — viz., the spinal marrow, running 

 through the length of the body, and a greatly enlarged mass in the head, called the brain. To 

 protect this most delicate and precious substance from external violence, it is incased in a strong 

 bony covering. That part which defends the spinal marrow consists of a number of perforated 

 bones, called vertebrae, joined to each other by cartilage, so as to make a continuous tube ; while 

 the casing of the brain consists of a box, more or less globular, called the skull. 



Through orifices at various points in these bones, ramifications of nervous matter proceed to all 

 parts of the body, these being the medium of sensation. The organs of the higher senses, as 

 sight, hearing, taste, and smelling, are situated in the immediate vicinity of the brain : the organs 

 of the sense of touch are usually distributed over the surface of the body, being more particularly 

 active, however, in certain parts of the skin. 



For voluntary change of situation, or power of motion, most animals of this division are fur- 

 nished with limbs, usually four in number, and ranged in pairs on the two sides. These, how- 

 ever, vary in form and function in the different classes. In man, the limbs consist of two legs and 

 two arms, the latter terminated by hands; in the monkey tribes, the arrangement is similar, but 

 all the four limbs are used for progression. In the bats, the arms and fingers arc prolonged into 

 wings. In the cetacea, the limbs are used for swimming only ; in the seal tribe, for swimming 

 chiefly, though they also serve for moving on the land in an awkward manner. In quadrupeds, 

 the four limbs are legs only ; in birds, there are two legs and two wings. In serpents, the limbs 

 are wanting. In fishes, the limbs consist of fins. It will be observed that in all these species, 

 without exception, this vertebral column, or backbone, is present, though in a few cases among 

 the lower members of the division, as the skate, for instance, it becomes cartilaginous, and in a few 

 others it is membraneous. In many species it is prolonged into a tail, which frequently seems 

 only an ornament, while in most cases it is useful, especially among climbing quadrupeds, as a 

 balance-pole in running along the limbs of trees, or as a hand to lay hold of them in swinging 



