TRANSVERSE SECTIONS OF A TEN MM. PIG EMBRYO 



Section through the Pancreatic Anlages (Fig. 140). The lesser peritoneal sac juts 

 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 ca 



R. vilelline or portal vein 

 Mesonephric dud 



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 bu 



Mesonephric duct 



Vein in body wall 

 L. umbilical artery 



Allantois and 

 urogenital sinus 



Notochord 



Rectum 



Spinal cord 



FIG. 141. Transverse section through the urogenital sinus and rectum of a 10 mm. pig embryo. 



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- 



