Development of the Third Day 205 



region is smaller and more nearly round in 

 cross-section, and is the oesophagus proper ; 

 its posterior limit is indicated by the position 

 of the lungs, whose development will shortly 

 be described. The fore-gut still ends blindly 



FIG. 67. DIAGRAM OF A PORTION OF THE DI- 

 GESTIVE TRACT OF A CHICK DURING THE FOURTH 

 DAY. (After Gotte, from Foster and Balfour.) 



The black inner line represents the hypoblast, the outer 

 shading the mesoblast. /^, lung diyerticulum. St, stomach. 

 /, two hepatic diverticula with their terminations united by 

 cords of hypoblast cells. /, diverticulum of pancreas. 



in front, as the mouth has not yet been 

 formed. 



It might here be mentioned that, during the 

 sixth day, the lumen of the oesophagus be- 

 comes completely closed for the greater part 

 of its length, and remains closed for two or 

 three days. Mention has already been made of 



