xxxi. i RUMINANT STOMACHS 743 



the hinder part of the vertebral column has almost become part of 

 the limb! 



The dentition of artiodactyls is highly specialized. The upper 



Fig. 491. Stomach of camels and ruminants. 

 A shows the relationship of the normal mammalian stomach (stippled) to that of ruminants. 

 The rumen (r.) represents the cardiac region, the reticulum {ret.) the body. The oeso- 

 phageal groove (g.) and omasum (0.) are derived from the lesser curvature as far as the 

 incisura angularis and the abomasum (ab.) represents the pyloric antrum; d. duodenum; 



oe. oesophagus. 



The omasum and abomasum are shown as if pulled downwards. In the camel zv.c. are 



the water cells. The abomasum is mostly lined with stratified squamous epithelium; 



fundic glands are found only in the dotted area. (Material for figure kindly supplied by 



Dr. A. T. Phillipson, partly after Pemkopf.) 



incisors are lost in later types, which crop by means of their gums. 

 The canines may form tusks. Premolars are not molarized, but an 

 efficient grinding battery is often provided by the very elongated, 

 hypsodont molars. These acquire a grinding surface by the develop- 

 ment of each of the four original cusps into a longitudinal ridge — 



