INTRODUCTION. 



3 



referred to as its type is the Horse, the Anatomy of v/hicli 

 animal, or Hippotomy, is primarily considered in this \vorK, 

 while the deviations from the type, which make up the compara- 

 tive branch of the subject, will be noted in their more important 

 features, as fully as the scope of the work will permit. 



VERTEBRATA. 



As all the domesticated animals belong to the sub-kingdom 

 Vertebrata, it is of importance to gain a clear idea of the lead- 

 ing characteristics of a vertebrate animal ; 

 and, except in one or two of the lowest 

 orders, these are well marked. 



The animal kingdom is divided into the 

 sub-kingdoms Invertebrata and Verte- 

 brata. As the names would imply, the latter 

 is distinguished from the former by its 

 members possessing a vertebral column, 

 or backbone, which forms, as it were, 

 the axis of the bony framework, supports 

 the head, and is placed dorsally, or in the 

 region of the back, extending from one end -^ 

 of the body to the other. It is pierced 

 throughout the greater part of its extent 

 by a canal called the neural canal, which 

 is continuous with a cavity in the, head 

 called the cranium. These cavities are 

 occupied by centres, from 

 the large series of nerves termed the 

 cerebrospinal system. Underneath the 

 backbone there is a second series of nerve- 

 centres — those of the sympathetic system. 

 Thus in a vertebrate animal there are system.-^yi^r NicnoLsoN. 

 two systems of nerves, whose centres are separated by a partition 

 cf bone. 



The remaining portion of the animal body may be regarded as 

 a second cavity, or canal, which contains, in addition to the 

 sympathetic system of nerves, the alimentary and the hcBmal 

 systems. The former runs the whole length _of ±he "body, being 

 a canal which gives passage to the food; the latter consists of 



Fig. 1. 

 A, Diagramatic transverse 

 section through the body of a 

 which radiate vertebrate. B, A simUar sec- 

 tion through a highly-organised 

 invertebrate animal. 



a, Neural Canal ; h, Cerebro 

 spinal nerve-centres ; c, Noto- 

 chord; d, Sympathetic nerve- 

 centres; e. Alimentary canal; 

 /, Visceral canal wall ; g. Haemal 



