4 INTRODUCTION. 



Lamprey — have no vertebral column, but they possess throughout 

 life a soft, gelatinous structure, the notochord, from which, in the 

 higher vertebrates, the column becomes early developed. These 

 may be regarded as exceptional or undeveloped forms. 



If we eliminate from the Vertebrata all the classes but the two 

 highest — Mammalia and Aves — we shall further localise our 

 subject, since these two classes contain all the animals, which, as 

 a rule, engage the attention of the veterinary anatomist, to whom 

 the first of the two is of by far the greater importance. 



domesticated mammals. 



It is sufficient to state that the Mammalia are characterised 

 by the females being provided with an apparatus which supplies 

 milk for the nourishment of their young after birth. 



The horse, ass, ox, sheep, goat, camel, llama, pig, elephant, dog, 

 cat, and rabbit are the mammalian vertebrates, usually included 

 in the term " domesticated animals." The first eight of these 

 belong to one of the most important of the natural orders, the 

 Ungulata, or hoofed animals. The camel, llama, and elephant, 

 not being domesticated, in the proper sense of the word, in 

 Europe, the scope of the present work will not permit separate 

 sections to be devoted to their description. 



UNGULATA. 



The Ungulata which includes the hoofed quadrupeds, is a very 

 large and important order, divided into two parts. One section, 

 the Perissodactyla, includes the animals having an odd number 

 of toes or digits ; the other, the Artiodactyla, containing those 

 with an even number. 



PERISSODACTYLA. 



EquidcB or Solidimgula. — The horse and ass are referred, in the 

 section Perissodactyla, to this family, which includes only the 

 two genera Equus and Asinus; their most prominent external 

 feature is the possession of only one perfect digit or finger on each 

 extremity. Apparently there is but one clearly defined species in 

 the genus Equus, the features presented by the varieties which are 

 know as " breeds " being, in all probability, due to the prolonged 

 influence of external circumstances, such as locality, treatment, 

 climate, and selection. In the Equidse the stomach is simple 

 and comparatively small. 



