TRANSVERSE SECTIONS OF A TEN MM. PIG EMBRYO 



137 



Section through the Pancreatic Anlages (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 



Dorsal aorta 



Inferior vena cava 



R. vitelline or portal vei 

 Mesonephric duel 



Post, cardinal vein 



Mesonephros 



L. vitelline vein 

 Dorsal pancreas 

 Liver 



Duodenum 



Ventral pancreas- 



FIG. 140. Portion of a transverse section through the pancreatic anlages of a 10 mm. pig 



embryo. X 22.5. 



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. 



Lower limb b 



Mesonephric due. 



Vein in body wall 

 L. umbilical artery 



Allantois and 

 urogenital sinus 



Rectum 



Notochord 



Spinal cord 



10 mm. pig embryo. 



FIG. 141. Transverse section through the urogenital sinus and recturr of 



X 22.5. 



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

 shows only the caudal end of a section, in the dorsal portion of which the mesonephroi 

 were sectioned at the level of the subcardinal anastomosis. A portion of the mesentery 

 is shown with a section of the colon. In the body wall are veins that drain into the umbili- 

 cal veins, and on each side are the umbilical arteries, just entering the body from the umbili- 



