STRUCTURE OF THE VERTEBRAL COLUMN. 87 



operations that uniformity, which is so remarkable a character- 

 istic of those which are under the guidance of pure Instinct 

 (ANIM. PHYSIOL., Chap. XIV.) There is evidently, among the 

 higher Vertebrata especially, a power of choice and of determina- 

 tion, guided by a perception of the nature of the object to be 

 attained, and of the means to be employed, constituting the 

 simplest form of the reasoning faculty. In Man, the reasoning 

 faculties seem to attain the highest perfection, that is compatible 

 with their connection with a material fabric ; the instinctive 

 propensities are placed under their subjection ; and all his acts, 

 except those immediately required for the maintenance of his 

 organic functions, are brought under their controul. But among 

 the lowest of the Yertebrated series, the operations of instinct 

 seem to be as predominant as in the Invertebrated classes ; 

 although, as they are inhabitants of the water, we are much less 

 acquainted with them. Hence we seem justified in asserting 

 that the Cerebrum is the instrument of intelligence ; and that the 

 high development of it is the chief characteristic of the Verte- 

 brated sub-kingdom. 



65. It is more satisfactory, however, to define this group by 

 the presence or absence of that internal skeleton, which is espe- 

 cially adapted for the protection of the nervous centres; namely, 

 the vertebral column. This essentially consists of a series of 

 bones, termed vertebras; through a perforation in the centre of 

 which, the spinal cord passes. When these bones are fitted 

 together, they form a continuous tube, in which 

 this important organ is lodged ; and they are con- 

 nected together, in the living state, by ligaments and 

 muscles, attached to the bony prominences or pro- 

 cesses with which they are furnished. In this 

 manner, the vertebral column possesses considerable 

 flexibility ; so that it may be bent into a curve, 

 without injury to the organ which it protects. If it had been 

 inflexible, the animal could not have propelled itself by any 

 movements of its body, but must have been entirely dependent 

 upon its limbs ; and if it had been composed of but a" small 

 number of bones, the spinal cord would have been liable to 



