104 



THE STUDY OF SIX AND TEN MILLIMETER PIG EMBRYOS 



stomach, and project into the pleural ccelom. The esophagus is short and widens 

 dorso-ventrally to form the stomach. The long axis of the stomach is nearly 

 straight, but its entodermal walls are flattened together and it has revolved on 

 its long axis so that its dorsal border lies to the left, its ventral border to the right, 

 as seen in transverse section (Fig. 106). 



Caudal to the pyloric end of the stomach, and to its right is given off from 

 the duodenum the hepatic diverticulum. Its opening into the gut is seen in the 

 ventral dissection (Fig. 92). The hepatic diverticulum is a sac of elongated oval 

 form which later gives rise to the gall bladder, cystic duct and common bile duct. 

 It is connected by several cords of cells with the trabeculas of the liver. 



The liver is divided incompletely into four lobes, a small dorsal and a large 

 ventral lobe on each side (Figs. 90 and 107). The lobation does not show in a 

 median sagittal section. The pancreas is represented by two outgrowths. The 



Lateral lingual anlage 

 Tuberculum impar 



Epiglottis 

 Arytenoid ridge 



Branchial arch I 

 Branchial arch II 



Branchial arch III 

 Branchial arch IV 

 Glottis 



FIG. 93. Dissection of the tongue and branchial arches of a 7 mm. pig embryo, seen in dorsal view. 



ventral pancreas takes origin from the hepatic diverticulum near its attachment 

 to the duodenum. It grows to the right of the duodenum and ventrad to the 

 portal vein. The dorsal pancreas takes origin from the dorsal side of the duo- 

 denum caudal to the hepatic diverticulum and grows dorsally into the substance 

 of the gastric mesentery (Figs. 100 and 108). It is larger than the ventral pan- 

 creas, and its posterior lobules grow to the right and dorsal to the portal vein and 

 in later stages anastomose with the lobules of the ventral pancreas. 



The intestine of both fore-gut and hind-gut has elongated and curves ven- 

 trally into the short umbilical cord where the yolk-stalk has narrowed at its point 

 of attachment to the gut. As the intestinal tube grows ventrally, the layers of 

 splanchnic mesoderm which attach it to the dorsal body wall grow at an equal 

 rate and persist as the mesentery. 



The cloaca, a dorso-ventrally expanded portion of the hind-gut gives off 



