35 



FIRST GREAT DIVISION OF THE ANIMAL KINGDOM. 



THE VERTEBRATE ANIMALS. 



The bodies and limbs of these being supported by a 

 frame-work composed of connected pieces moveable 

 upon each other, they have the more precision and 

 vigour in their movements : the solidity of this support 

 permits of their attaining considerable size, and it is 

 among them that the largest animals are found. 



Their more concentrated nervous system, and the 

 greater volume of its central portions, impart more 

 energy and more stability to their sentiments, whence 

 result superior intelligence and perfectibility. 



Their body always consists of a head, trunk, and 

 members. 



The head is formed by the cranium, which incloses 

 the brain, and by the face, which is composed of the 

 two jaws and the receptacles of the organs of sense. 



Their trunk is supported by the spine of the back 

 and the ribs. 



The spine is composed of vertebrae moveable upon 

 each other, of which the first supports the head, and 

 which have an annular perforation, forming together a 

 canal, wherein is lodged that medullary production 

 from which the nerves arise, and which is called the 

 spinal marrow. 



The spine, most commonly, is continued into a tail, 



extending beyond the hinder limbs. 



The ribs are semicircles, which protect the sides of the cavity of the trunk : they 



are articulated at one extremity to the vertehne, and are ordinarily attached in front to 



the breast-bone ; but sometimes they only partly encircle the trunk, and there are 



genera in which they are hardly visible. 



There are never more than two pairs of limbs; but sometimes one or the Other is 

 wanting, or even both : their forms vary according to the movements which they have to 

 execute. The anterior limbs may be organized as hands, feet, wings, OT fins; the 



posterior aa feet, or instruments for swimmini 



i) 2 



Fig. 1. 



