XIlI 



PHYLUM CHORDATA 



571 



of this organ reaches its extreme limit in the ruminant Ungulata 

 and in the Cetacea. In a typical Ruminant (Fig. 1198, E, Fig. 

 1199.), such as a sheep or an Ox, the stomach is divided into four 

 chambers — the rumen or paunch, the reticulum, the psalterium, 



Fig. 1198.— Different forms of the stomach In Mammals. A, Dog ; B, SIus decumanus ; 

 V, Mns musculus ; D, Weasel ; E, scheme uf the ruminant stomach, the arrow with 

 the dotted line showing the course taken by the food ; F, bum^n stomach ; G, Camel ; 

 B, Echidna aculeata ; /, Bradypus tridactylus. A. (in E and G) ahomasum ; Ca. 

 cardiac end ; Cma, greater curvature ; Cmi, lesser curvature ; J)ii. duodenum ; MB, cpecum ; 

 0, psalterium ; Oe. oesophagus ; 'P. pylorus ; R. (to the right in Fig. E) rumen ; R (to the left 

 inFig. E) reticulum; Sc. cardiac division ; Sj3, pyloric division ; W. Z, water-cells. (From 

 Wiedersheim's Comparative Anatomy.) , 



and the ahomasum, or rennet-stomach. The first of these (Fig. 

 1199, I) is much larger than the rest; its mucous membrane 

 is beset with numerous short villi. The reticulum (c), which 

 is much smaller than the rumen, has its mucous membrane 



