INTRODUCTION. 3 



referred to as its type is the Horse, the Anatomy of which 

 animal, or Hippotomy, is primarily considered in this WorK, 

 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. 



VEllTEBRATA. 



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 ^^°-*- 



,, , ^, , ~, ... A, Diagramatic transverse 



.called the cramum. ihese cavities are section through the body of a 

 occupied by centres, from which radiate vertebrate b a simUar sec- 



^ •' . ' tion through a highly-organised 



the large series of nerves termed the invertebrate animal. 

 cerehro-s-pinal system. Uoderneath the ,p";aT'n"1e'?cTntrL^; ?no[o. 

 backbone there is a second series of nerve- chord; a, sympathetic nerve- 



,7 .. , centres; €, Alimentary canal; 



centres — those oi the sympathetic system. /, visceral canaiwaii;g,Hffimai 

 Thus in a vertebrate animal there are system.-^/ier NicnoLsoN. 

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

 of 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 kcemal 

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

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



