134 



THE STUDY OF SIX AND TEN MILLIMETER PIG EMBRYOS 



ulum. The great omentum of the stomach is larger than in the previous section and to its 

 right, in the phca venae cavje, lies the inferior vena cava. Ventral to the inferior vena cava 

 is a section of the portal vein. The ventral and dorsal lobes of the liver are now separate and 

 in the right ventral lobe is embedded the saccular end of the hepatic diverticulum which forms 

 the gall bladder. To the right of the stomach, the diverticulum is sectioned again just as it 

 enters the duodenum. Ventrally the left umbilical vein is entering the left ventral lobe of the 

 Hver. It is much larger than the right vein, which still courses in the body wall. On the 

 left side of the embryo the spinal nerve shows in addition to its dorsal and ventral rami a sym- 

 pathetic ramus, the fibers of which pass to a cluster of ganghon cells located dorso-lateral to the 

 aorta. These cells form one of a pair of sympathetic ganglia and are derived from a spinal 

 ganglion. 



Sfnial cord 



Notorhnrd 

 Mesoiii'pliri>\ 



Plica vence cava: 



Inferior vena cam 



Lesser peritoneal sar 



Portal vein 

 Hepatic diverticulu iii 



R. umbilical 



Sympathetic ramus 

 Dorsal aorta 

 Dorsal mesogaslrium 



M esonephric duel 

 Stomach 



Ventral lobe of liver 

 nmhilical vein 



Fig. 139.— Transverse section through the hepatic diverticulum of a 10 mm. pig embrj'o. X 22.5. 



Section through the Pancreatic Aniages (Fig. 140).— The lesser peritoneal sac just 

 above the level of this section has opened into the peritoneal cavity through the epiploic 

 foramen (of Winslow). The mesonephric ducts are now prominent ventrally in the meso- 

 nephroi. The duct of the dorsal pancreas is sectioned tangentially at the point where it takes 

 origin from the duodenum. From the duct the lobulated gland may be traced dorsad in the 

 mesentery. To the right of the dorsal pancreatic duct is a section of the ventral pancreas, 

 which may be traced cephalad in the series to its origin from the hepatic diverticulum. Dorsal 

 to the ventral pancreas is a section of the portal vein. The inferior vena cava appears as a 

 vertical slit in the dorsal mesentery. 



Section through the Urogenital Sinus and the Lower Limb Buds (Fig. 141).— 

 .The figure shows only the caudal end of a section, in the dorsal portion of which the meso- 



