86 VERTEBRAL COLUMN. 



growing, and of being reproduced after injury, like any other 

 part of the living tissue ; being copiously supplied with blood- 

 vessels, which penetrate into their interior. These bones give 

 support, and afford points of attachment, to the soft parts, in the 

 limbs (where they exist) as well as in the trunk ; but the former 

 are not unfrequently wanting, as in Serpents : and we must look 

 in the trunk, therefore, for that peculiar arrange- 

 ment which is characteristic of this division of 

 the Animal Kingdom. The back-bone, as it is 

 commonly termed, is found in all Vertebrated 

 animals ; though in a few among them (the 

 lowest Fishes) it is very imperfect ( 53). It 

 consists of several pieces jointed together, so as 

 to possess great flexibility; whilst they are so 

 firmly connected by ligaments, that they cannot 

 easily be torn asunder or displaced. The number 

 of these pieces varies considerably ; in Man there 

 are only 33 ; in some long- tailed Mammals there 

 are more than 70 ; but in many Serpents there 

 are several hundred. Each of them is termed a 

 vertebra; and the whole structure, composed of the 

 ^JRAif coIuM TE ~ lin ^' e( ^ Ver tehra3, i s termed the vertebral column 

 (fig. 26). The ordinary character of the vertebras 

 is, that each is perforated by an aperture, which, united to the 

 corresponding apertures of those above and below it, forms 

 a continuous canal ; and in this canal, one of the most im- 

 portant parts of the nervous system, the spinal 

 cord (commonly but erroneously termed the spinal 

 marrow), is contained. The solid portion of the 

 vertebra (fig. 27, a) is termed its body; and the 

 projections, b and c, are termed its processes, the 

 former spinous, the latter transverse. The row 

 of spinous processes forms the ridge which we 

 P ass i n g down the back; it is seen on the 

 right-hand side of fig. 26. To the. transverse 

 processes the ribs are attached. The vertebral column is ex- 

 panded (as it were) at its upper extremity, to form the skull ; 

 in the large cavity which it contains, the brain is lodged ; and 

 its bones are so arranged as to give protection to the organs of 

 sense also. At the opposite extremity we see it contracted 

 into the tail; which is composed of a series of vertebrae 



