NO. II DIGESTIVE CANAL OF AMERICAN ALLIGATOR — REESE 1 3 



lies a small, circular opening, the bile duct, bd. Its epithelium con^ 

 sists of a sing-le layer of columnar cells. In more anterior sections 

 the bile duct is larger in cross section, being about one-half the 

 diameter of the oesophagus. As has been said it ends blindly at a 

 jxiint a short distance anterior to the antero-ventral edge of the liver. 

 A few sections caudad to the one under discussion the bile duct con- 

 nects with the liver, iigure 6a, bd' ; and some distance caudad to 

 this the duct opens, bd", into the duodenum so close to the opening, 

 pan', of the pancreas that it is difficult to determine whether the 

 latter organ has a separate opening into the duodenum or opens into 

 the bile duct. 



At some distance ventrad to the structures just described the 

 intestine is cut, by the plane of the section, in two places, i. The 

 more dorsal of these is inclosed and has, under this magnification, 

 the same appearance as the duodenum, d; a higher magnification, 

 however, shows that its epithelium consists of a single layer of tall, 

 rather clear, columnar cells. The more ventral of the two sections, 

 above mentioned, which is continuous with the dorsal section a very 

 short distance caudad to this point, is in the region that opens to the 

 yolk — in fact a number of yolk-granules, y, may be seen in the 

 opening. The epithelium of this part of the intestine consists of a 

 single layer of clear, columnar cells, which, around the borders of the 

 opening, are thrown into numerous folds and are almost pf goblet 

 form. 



Figure 6h represents a section through the plane 820 of figure 6a. 

 The section is caudad to one lung and cuts the extreme tip of the 

 other, /;/. The liver, li, and pancreas, pan, are seen at the side of 

 the stomach, i', here cut through its greatest transverse diameter. 

 The epithelium of the stomach varies somewhat in thickness and 

 consists of two or three layers of cells, the variation in thickness 

 being due to a variation in the length of the cells rather than to a 

 variation in the number of layers. 



Ventrad to the stomach the intestine, i is cut in three places, of 

 which the most dorsal section is the largest. The epithelium of these 

 intestinal sections, especially the lower two, consists of usually a 

 single layer of columnar cells which are clearer than those of the 

 stomach. A fairly thin mesentery, vis, supports this region of the 

 intestine. 



In the region of the posterior appendages, pa, the section passes 

 through the hindgut, kg, and allantois, al. The former is of about 

 the same size as the more anterior sections of the intestine, but its 

 epithelium is less clear and is composed of two or more layers of 

 cells. The allantois is cut near its opening into the hindgut ; its walls 



