318 



EODENTIA. 



large cul de sac, which projects upwards along the side of the oesophagus, and inter- 

 nally its walls are seen to he thick and to he quite different from the remainder 

 of the stomachic wall. To the right of the oesophagus, there is a rounded 

 eminence in the position of the sack which occurs in the stomach of the voles, 

 and which prohahly will he detected also in fresh stomachs of Siphneus. Imme- 

 diately below, and to the right of the swelhng, there is a contraction which marks 

 off the left limit of the pre-pyloric sack which is cylindrical and elongated. 

 Prom this contraction to the base of the left cul de sac is the great cavity 

 of the stomach. 



The stomach of R. badius presents some well-marked modifications on these 

 foregoing characters, and they are the more remarkable because the external 

 features of the two species are so alike that they could not be supposed to 

 imply internal structural differences of so considerable importance. In this form, 

 the left cul de sac is evidently suppressed, and the swelling to the right of 



Fig. 12. — Stomacli of Rhizomijs badius, Hodg. Nat. size. 



the oesophagus is replaced by the lesser curvature which is extremely short, as 

 there is a sUght constriction at its right end and also on the right wall of the 

 stomach on a level with the lesser curvature, marking the commencement of the 

 pre-pyloric sack. With the exception of this last cavity, the stomach of R. badius 

 is simple. 



On laying open the stomach of II . pruinosus, the longitudinal folds of the oeso- 

 phagus, as I have stated, are seen to be prolonged downwards, along the right margin 

 of the base of the cul de sac, in the form of a distinct groove or canal similar to that 

 which occurs in the stomach of Siphneus and of the Lemmings, and which is 

 analogous to the canal in the ruminant stomach. The termination of the canal is 

 marked by a raised border which is a continuation of the fringe which defines the 

 limit to the right of the left cul de sac. A similar fringe occurs in the stomach of 

 Siphneus. The walls of the left sack are thicker than any other part of the stomach, 



