The Digestive System 



187 





power drawing of the posterior region is shown in 

 Figure 52. The anterior and posterior regions of 

 the large intestine do not differ from each other 

 sufficiently to make it worth while to represent 

 both by drawings. Had an entire section through 

 either region been drawn it 

 would be seen that the wall 

 is of very different thickness 

 in different places, as was 

 noted in connection with the 

 small intestine ; the posterior 

 section was drawn where the 

 wall was thin. 



It might be supposed that 

 in the feeding season the fecal 

 matter in the posterior re- 

 gion of the rectum would 

 stretch the walls sufficiently 

 to obliterate largely the 

 prominent folds seen in Fig- 

 ure 52, but such does not 

 seem to be the case. The 

 usual layers of the vertebrate intestine are present. 



The epithelium, shown under high magnifica- 

 tion in Figure 53, is of the same character and thick- 

 ness throughout, except that as the anal aperture is 

 approached the columnar epithelium changes into 

 the stratified variety. It consists of very tall and 

 narrow columnar cells apparently in one layer, 

 though it is difficult to be sure of this. With an 



.!-~-^.;iX"^S>XrS?-' 



mm 



FIG. 53. The epithelium 

 of the anterior region of the 

 rectum of the hibernating ani- 

 mal, under high magnifica- 

 tion; e, epithelium; tp, 

 tunica propria. 



