18 PRINCIPLES OF VETERINARY SCIENCE 



The mammals form a class, in which we are particularly inter- 

 ested, comprising all large domesticated animals. Mammals 

 are air-breathing, warm-blooded, produce their young alive and 

 nourish them for a variable period on a secretion from the mam- 

 mary glands, and have appendages of the skin in the form of 

 hairs. They are divided into a great many natural orders. 



Most farm animals belong to the 

 order of ungulates. 



The ungulates are quadrupeds hav- 

 ing molar teeth adapted for crushing 

 and grinding food, possessing a com- 

 plete set of milk teeth, being destitute 

 of a clavicle or collar-bone, never 

 developing five digits, and having 

 the terminal bone of each digit in- 

 vested by a thick horny covering 

 or hoof. They are divided into two 

 suborders: the perissodactylates, 

 which have an odd number of toes 

 or digits; the artiodactylates, which 

 have an even number. 



The perissodactylates include only 



two genera and species: the equus to 



Diagrammatic which the horse belongs; the asinus 



transverse section through body to w hj c h the ass belongs, 

 of a vertebrate: c.v., cavity for „,, . , . , . . , , 



visceral organs; c.n., cavity for * ne amodactylates include among 

 central nervous organs; n., others the following genera and 

 ItTm^B, S s3r h s e et species:theruminantsorcud-chewing 

 tion of invertebrate : c.v., cavity animals, which embrace the ox, sheep, 

 for visceral organs; ».(., nerve g0 at, camel, and llama; the omnivora, 



which embrace the pig. 



The ruminants remasticate their feed and are cloven hoofed, 

 having two well developed digits on each foot. 



The omnivora have teeth that are adapted to the mastication 

 of all kinds of food and are provided with four digits on each 

 extremity, two of which are long and two short. 



THE CHEMICAL CONSTITUTION OF THE ANIMAL BODY 



It is practically impossible to determine the chemical composi- 

 tion of living organic matter because changes are constantly 



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