TRANSVERSE SECTIONS OF A SIX MM. PIG EMBRYO III 



is rotated to the left, its ventral wall to the right. The liver shows a pair of dorsal lobes and 

 contains large blood spaces and networks of sinusoids lined with endothelium. Ventral 

 to the liver, the tips of the ventricles are seen. 



Section through the Hepatic Diverticulum (Fig. 112). The upper limb buds are 

 prominent in this section. The mesonephric folds show the tubules and glomeruli of the 

 mesonephroi, and the posterior cardinal veins are connected with the mesonephric sinu- 

 soids. From the dorsal attachment of the liver there is continued down into this section 

 a ridge on the dorsal body wall just to the right (left in figure) of the mesentery. In this 

 ridge lies a small vein which connects cranially with the liver sinusoids, caudally with the 

 right subcardinal vein. As it later forms a portion of the inferior vena cava, the ridge in 

 which it lies is termed the plica vena cava, or caval mesentery. The right dorsal lobe of 

 the liver contains a large blood space into which the portal vein opens. The duodenum is 

 ventral to the position occupied by the stomach in the previous section. There is given 

 off from it ventrad and to the right the hepatic diverticulum. In the sections higher up, 

 small ducts from the liver trabeculae may be traced into connection with it. In the left 

 ventral lobe of the liver, a large blood space indicates the position of the left umbilical 

 vein on its way to the ductus venosus. 



Myotome J||{Hl||g|i Spinal cord 



, A 



L. post, cardinal vein 



limb btld 



'Dorsal pancreas 



' vitelline veln 



Duodemim 

 Distal end of hepatic diverticulum p'' L< umbilical vein 



Ventral pancreas 

 FIG. 113.- Transverse section through the dorsal pancreas of a 6 mm. pig embryo. X 26.5. 



Section through the Dorsal Pancreas (Fig. 113). At this level the upper limb buds 

 still show; the mesonephroi are larger and marked by their large glomeruli. The right 

 posterior cardinal vein is broken up into mesonephric sinusoids. The vein in the plica 

 venae cavae will, a few sections lower, connect with the right subcardinal vein. The an- 

 lage of ^ the dorsal pancreas is seen extending from the duodenum dorsad into the mesen- 

 chyme of the mesentery. It soon bifurcates into a dorsal and right lobe, of which the latter 

 is slightly lobulated. Ventro-lateral to the duodenum the anlage of the ventral pancreas 

 is seen cut across. It may be traced cephalad in the series to its origin from the hepatic 

 diverticulum. To the right of the ventral pancreas lies the portal vein (at this level a por- 

 tion of the right vitelline). To the left of the dorsal pancreas is seen the remains of the 

 left vitelline vein. The ventral lobes of the liver are just disappearing at this level. In the 

 mesenchyme that connects the liver with the ventral body wall lie on each side the umbili- 



JPT 



