THE LATER DEVELOPMENT OF THE CHICK 335 



Although really derived from the embryonic fore-gut, we 

 may include here certain details in the later development of 

 of the oesophagus and stomach, the formation of which was 

 mentioned above. The stomach and intestine extend through 

 the body cavity, from the dorsal wall of which they are suspended 

 by a double mesodermal fold, the dorsal mesentery and meso- 

 gastrium, which represents the original dorsal fusion of the lateral 

 splanchnopleural folds involved in the establishment of the 

 intestinal groove and tube. The similarly formed ventral 



FIG. 132. Partially dissected viscera of the chick, from the right side. 

 After Duval. A. Of a six-day chick, enlarged slightly less than six times. 

 B. Of a thirteen day chick, enlarged two and one-half times, showing the elon- 

 gated intestine and its extension into the umbilical stalk, a, Right auricle; aZ, 

 allantois; as, abdominal air sac; 6, bulbus arteriosus; c, caecal processes; d, loop 

 of duodenum; dj, duodenal-jejunal flexure (a relatively fixed point during the 

 elongation of the intestine) ; /, fore-limb bud (cut through) ; g, gizzard; go, gonad ; 

 A, hind-limb bud (cut through) ; i, loops of small intestine; I, liver; Ig, lung; II, 

 left lobe of liver; h, left ventricle; M, rudiment of Miillerian duct (tubal ridge) ; 

 p, pancreas; r, rectum; rl, right lobe of liver; rv, right ventricle; s, yolk stalk; 

 u, umbilical stalk; W, Wolffian body or mesonephros. 



mesentery disappears immediately after its formation, save in 

 the region of the stomach and liver, where it forms the gastro- 

 hepatic ligament. 



The oesophagus elongates with the neck, and during the 

 seventh to eleventh days is closed just back of the glottis by 

 cells proliferated from its wall. The crop appears as a posterior 

 dilation of the oesophagus just in front of the stomach. During 

 the fifth to seventh days the enlarging stomach becomes differ- 



