l8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 56 



forms the greater part of their thickness, muscle fibers are beginning 

 to differentiate. The epithehal layer also is thicker than in the 

 oesophagus ; it consists of tall columnar cells that, at places, are 

 thrown into small folds, figure 71. These folds, even under the 

 low magnification used, are more evident than is shown in the 

 present figure. The pylorus, py, is wide and, as has been noted in 

 connection with figure 7, is situated far cephalad to the caudal end 

 of the stomach. It opens into the side rather than into the end of the 

 duodenum, which projects cephalad as a short blind pouch, d. The 

 stomach and duodenum, in this section, are almost completely sur- 

 rounded by the liver, li. 



Figure 70 represents a section through the plane 680 of figure 7. 



The stomach, i' , which is cut through its middle region, is some- 

 what larger "than in the preceding figures, though its walls have 

 about the same character. Its outer walls are continuous, to a con- 

 siderable extent, with the tissue of the surrounding body wall, espe- 

 cially in the region just caudad to the plane of the present section. 



The duodenum, being cut through a double loop (see figure 7), is 

 seen in two places, dorsally where it is cut through the edge of one 

 loop, and ventrally where it is cut square across. In both sections 

 the structure is the same, as might be expected, figure 7J. The sur- 

 rounding mesoblast is dififerentiated into muscle fibers, figure 7J, ml, 

 which form a fairly distinct layer; inside of this layer is a tall 

 columnar epithelium, cp', which is thrown into prominent folds. A 

 thin layer of mesoblast, probably the submucosa, sL lies beneath the 

 epithelium and projects up into the folds. About ten or twelve folds 

 are seen in any one section ; only the larger ones are well seen in 

 figure 70. 



Figure 7E shows a section through the plane 770 of figure 7. 

 It is in the region of the umbilicus, ;;, and the extreme caudal end of 

 the stomach which has been called the gizzard, g^. The small size 

 of the gizzard is due to its being cut near its caudal margin. The 

 enteron is here cut in no less than seven places : the reason for this 

 will be evident on examination of the plane of the section as shown 

 in figure 7. Dorsal to the gizzard the section cuts the so-called 

 caecum, cc, a little nearer its anterior end than is shown in figure 7. 

 The duodenum, (/, is cut at five points, and has about the same 

 structure as in the preceding figure. The character of the duodenal 

 loops that causes the rather curious appearance of the present figure 

 will be readily understood by reference to figure 7, though the 

 reconstruction is not mathematically accurate. The ventral pro- 

 jection of the lower loops of the duodenum into the umbilicus is seen 

 both in the present figure and in the reconstruction. The loop of 



