ZOOLOGY. 



FIRST GREAT DIVISION. 

 VERTEBRATA. 



THE highest forms of animal structure are distin- 

 guished by having the nervous matter, the source of all 

 sensation and intelligence, concentrated into a single 

 mass, which may, however, be conveniently considered 

 as consisting of two parts, viz., a long slender column, 

 the spinal marrow, running through the length of the 

 body ; and a greatly enlarged mass, situated at its 

 front extremity, and called the brain. To protect 

 this most delicate and precious substance from exter- 

 nal violence, it is encased in a strong bony covering ; 

 that part which defends the spinal marrow, taking 

 the form of a number of small perforated bones, call- 

 ed vertebra, jointed to each other by cartilage, so as 

 to make a continuous tube, while the covering of the 

 brain forms a box, more or less globular, called the 

 skull. Through orifices in these bones ramifications 

 of nervous matter proceed to all parts of the body, 

 and are the medium of sensation. The organs of the 

 higher senses are situated in the immediate vicinity 

 of the brain. 



VOL. I. B 



