I70 The Alligator and Its Allies 





cm 



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 

 4 1 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 

 tissue studied thrown into 

 less com.plicated folds than 

 in the anterior region, and is 

 not so thick. 



The submucosa, sni, if the 

 entire layer maybe so called, 

 has about the same thick- 

 ness and structiu"e 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 



1. 





Fig. 42. A transsection 

 through the posterior region 

 of the oesophagus of the 

 hibernating animal, under low 

 magnification; e, epithelium; 

 cm, circular muscles; bn, 

 longitudinal muscles; mtn, 

 muscularis mucosa; sm, sub- 

 mucosa; s, serosa. 



