THE MUSEUM 



NATURAL HISTORY 



ZOOLOGY. 



VERTEBRATE ANIMALS-(vERTEBRATA.) 



WHEN the immortal Cuvier published his new arrange- 

 ment of the Animal Kingdom, he divided all animals 

 into four principal sections, which we still find adopted, 

 with some modifications, by most naturalists. The 

 changes which have been made in the contents of 

 these great divisions, in accordance with the progress 

 of zoological science since the death of the great 

 French comparative anatomist, have principally affected 

 the three lower groups established by him, and the 

 limits of his first and highest division of animals, that 

 of the Vertebrata, have remained without alteration. 

 This, indeed, is no more than might have been ex- 

 pected. The vertebrate animals are those whose 

 existence has always, from various circumstances, been 

 pressed most forcibly upon the notice of mankind. 

 Vertebrate animals furnish the greater part of our 

 Jaily food, and amongst them are to be found our 

 most dangerous enemies, so that the mere instinct of 

 self-preservation must have early led even the uncivi- 

 lized man almost unconsciously to the study of their 

 natural history. Hence, the knowledge of the differ- 

 ences and agreements in the structure of these crea- 

 tures had made great progress, even in the popular 

 mind, at a period when the greatest philosophers 

 knew little of the remainder of the animal kingdom ; 

 and Linnaeus, in dividing the whole of animated 

 nature into six classes, gave no fewer than four to the 

 creatures which we now distinguish as Vertebrata. 



The name of Vertebrata or Vertebrate animals, given 

 to this great section of the Animal Kingdom, has 

 reference to one of its principal characters, namely, the 

 possession of a backbone (spine or vertebral column), 

 composed of numerous joints (vertebrae) attached firmly 

 to each other, but in such a way as, in most cases, to 

 insure more or less flexibility. 



The office of this bony column is twofold. In the 

 first place, by its enlargement into the hollow case 

 called the skull, and by the presence of apertures in 

 each of its joints, which, when placed in their proper 

 position, form a continuous tube or canal running 

 down the back of the animal it furnishes a protection 

 for the brain and spinal marrow (spinal cord), the 

 VOL. I. 



great centre of the nervous system, which in these 

 creatures attains a high degree of development In 

 the second place, by affording support to numerous 

 other bones, varying in form and arrangement accord- 

 ing to the duties they have to perform, it consti- 

 tutes the centre of the skeleton of these animals a sort 

 of bony framework which at the same time serves 

 to protect the more important internal organs, and 

 to furnish solid points of attachment for the muscles 

 by which the movements of the various parts are 

 effected. 



This framework of bones consists, in addition to 

 the skull and spinal column already referred to, of the 

 ribs, and of the bones of the limbs the former, as is 

 well known, constituting a series of long curved bones 

 which inclose the cavity of the chest, and are for the 

 most part movably articulated to the vertebrae on each 

 side. The opposite extremities of the ribs are also 

 usually united to a single bone, which occupies the 

 centre of the anterior or inferior surface of the chest, 

 called the breastbone (or sternum) ; and in most air- 

 breathing Vertebrata the whole framework of the chest 

 is capable of moving by the action of the muscles 

 attached to the ribs, in such a manner as to increase 

 or diminish the size of the cavity inclosed by them, 

 thus causing the lungs to be alternately filled with 

 and emptied of the air necessary for respiration. The 

 vertebrae which bear the ribs are usually distinguished 

 by several peculiarities of construction from those of 

 the other parts of the spinal column ; they are called 

 dorsal vertebra, or vertebrae of the back; those in 

 front of them, forming the neck, are called cervical 

 vertebrae, and those behind them, which are usually 

 of great size, are called lumbar vertebrae, or vertebrae of 

 the loins. The latter are followed by the vertebrae 

 which support the hinder extremities ; and these again, 

 in most of these animals, by a number of vertebrae, 

 gradually diminishing in size and completeness, which 

 form the tail. These are the caudal vertebrae. 



Of limbs in the Vertebrata there are never more 

 than two pairs. The anterior limbs are usually attached 

 to the body by being articulated to a pair of flat bones 



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