RUMINATION 



281 



in the upper jaw, and very usually there are none. As a 

 general rule the third and fourth metacarpals and metatarsals 

 become united to form a cannon bone. To this there is but one 

 exception, the African Hyomosclnis. Moreover, the second and 

 fifth digits are nearly always rudimentary, and may practically 

 disappear altogether. Here again the Tragulidae are an excep- 

 tion. The Eumiuantia are so-called on account of the fact that 

 they " ruminate," that is, after the food lias been rapidly 



Fig. 146. — Stomach of Rummant opened to show the internal structure, a, Oesophagus ; 

 b, rumen ; c reticxilum ; d, psalterium ; e, abomasnni ; /, iluodeniim. (After 

 Flower and Lydekker.) 



swallowed, it is forced back up the gullet and more thoroughly 

 masticated. Associated with this is a complex stomach, which 

 is divided into several compartments. This stomach has at least 

 three compartments, as in the Tragulidae ; but it has usually four. 

 Its characters are illustrated in Fig. 146. The majority of the 

 Selenodontia possess horns, which are partly formed of solid 

 protuberances of the frontal bones. In the Giraffe they are 

 somewhat different. 



This group may be divided into — A. Teagulina, Chevro- 

 tains ; B. Tylopoda, Camels, Lamas ; and C. Pecoea, Deer, Ante- 

 lopes, Oxen, Giraffes, Goats, Sheep. 



A. TRAGULINA. 



As the TraguLina are undoubtedly the most ancient of the 

 Selenodontia it will be logical to commence with an account 

 of them. 



