The Digestive System 



173 



even in this anterior region are not everywhere 

 present; possibly they are arranged in bands, but 

 the material at hand was not suf- 

 ficient to determine this. As was 

 noted above, cilia are wanting in the 

 posterior region. 



The only differences noted in the 

 anterior region of the oesophagus 

 between the feeding and the hiber- 

 nating conditions are in the muscu- 

 laris mucosa and the epithelium. 

 As was noted above, the muscularis 

 mucosa is practically absent in the 

 hibernating stage, being represented 

 only by a few small, scattered bundles 

 of longitudinal muscle fibers ; while 

 in the feeding stage there is a narrow 

 but fairly distinct layer to represent 

 the muscularis mucosa. 



The difference in the appearance 

 of the epithelium is not striking. 

 The nuclei are somewhat larger in 

 the feeding stage and, instead of 

 being crowded into a basal and a 

 median zone, as noted in the hi- 

 bernating conditions, they form a dense basal 

 zone, but show no indication of medial zone. From 

 the dense basal zone the nuclei become more scat- 

 tered towards the free surface and are rarely found 

 closer to the surface than is shown in Figure 44. 



FIG. 44. The 

 epithelium of the 

 anterior region 

 of the oesophagus 

 of the feeding 

 animal, under 

 high magnifica- 

 tion. 



