170 The Alligator and Its Allies 



mm 



The serosa, s, is here quite indistinct. It con- 

 sists of a slightly vascular 

 connective tissue which can- 

 not be distinctly differenti- 

 ated from the connective 

 tissue of the longitudinal 

 layer. 



In the posterior region of 

 the oesophagus, as may be 

 seen by comparison of figures 

 41 and 42, the wall as a whole 

 is about one third thicker 

 than in the anterior region 

 just described, though how 

 much of this difference is due 

 to different degrees of dis- 

 tension or contraction it is 

 hard to say. 



The epithelium, e, is in the 



Fie, 42. A transsection tisSU6 Studied thrown into 

 through the posterior region less Complicated folds than 



of the oesophagus of the j n the anterior region, and is 



hibernating animal, under low 



magnification; e, epithelium; not SO tniCK. 



cm, circular muscles; Im, The submUCOSa, Sm, if the 



longitudinal muscles; mm, 1 , 11-1 



muscuiaris mucosa; sm, sub- entirelayer maybe so called, 

 mucosa; s, serosa. has about the same thick- 



ness and structure as in the 



more anterior region; but instead of the small 

 and widely scattered bundles of longitudinal 

 muscle fibers there is a distinct layer of muscle 



