THE STUDY OF SIX AND TEN MILLIMETER PIG EMBRYOS 



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. 97). The hepatic diverticulum is a sac 

 of elongated oval form from which the liver and part of the pancreas take 

 origin, and which later gives rise to the gall bladder, cystic duct, and com- 

 mon bile duct. It is connected by several cords of cells with the trabeculae 

 of the liver. 



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

 large ventral lobe on each side (Figs. 95 and 112). The lobation does not 

 show in a median sagittal section. The pancreas is represented by two 

 outgrowths. The ventral pancreas originates from the hepatic diverticu- 

 lum near its attachment to the duodenum (Fig. 96). It grows to the 



Lateral lingual anlage 

 Tuberculam impar 



Epiglottis 

 Arylenoid ridge 



Branchial arch I 

 Branchial arch 2 



Branchial arch 3 

 Branchial arch 4 

 Glottis 



FIG. 98. Dissection of the tongue and branchial arches of a 7 mm. pig embryo, seen in dorsal 



view. X 15. 



right of the duodenum and ventral to the portal vein. The dorsal pancreas 

 takes origin from the dorsal side of the duodenum, caudal to the hepatic 

 diverticulum and grows dorsally into the substance of the gastric mes- 

 entery (Figs. 105 and 113). It is larger than the ventral pancreas, 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 

 ventrally into the short umbilical cord where the yolk stalk has narrowed 

 at its point of attachment to the gut (Fig. 96). As the intestinal tube 

 grows ventrad, 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 cephalad and ventrad the allantoic stalk. This is at first a narrow tube, 

 but soon expands into a vesicle of large size, a portion of which is seen in 

 Fig. 96. Dorso-laterad the cloaca receives the primary excretory (mesoneph- 

 ric) ducts. The hind-gut is continued into the tail as the tail gut, or 

 postanal gut, which dilates at its extremity as in the 7.8 mm. pig described 



