XIII 



PHYLUM CHORDATA 



539 



is much smaller than the rumen, has its mucous membrane 

 raised up into a number of anastomosing ridges, giving its wall 

 the appearance of a honeycomb with shallow cells. From the 



FIG. 1139. Different forms of the stomach in Mammals. A, Dog ; B, Mus decumanus ; 

 C, Mus musculus; J), Weasel; E, scheme of the ruminant stomach, the arrow with 

 the dotted line showing the course taken by the food ; F, human stomach ; G, Camel ; 

 H, Echidna aculeata; 7, Bradypus tridactylus. A. (in E) abomasnm ; Ca. cardiac 

 end ; Cma, greater curvature ; Cmi, lesser curvature ; Du. duodenum ; MB, ccecum ; 

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

 in Fig. E) reticulum ; Sc. cardiac division ; Sp, pyloric division ; W. Z, water-cells. (From 

 Wiedersheim's Comparative Anatomy.) 



aperture by which the reticulum communicates with the rumen, 

 to that with which it communicates with the psalterium, runs 

 a groove bounded by a pair of muscular ridges, which are capable 

 of closing together in such a way as to convert the groove into 

 a canal. The mucous membrane of the psalterium (d) is raised 



