TRANSVERSE SECTIONS OF A TEN MM. PIG EMBRYO. 



125 



pottion of the right are persistent. The left vitelKne vein, fused with the right, 

 courses from the yolk sac cephalad of the intestinal loop. Near a dorsal anas- 

 tomosis between the right and left vitelline veins, just caudal to the duct of the 

 dorsal pancreas, the left receives the superior mesenteric vein, a new vessel arising 

 in the mesentery of the intestinal loop. Cranial to its junction with the superior 

 mesenteric vein, the left vitelline, with the dorsal anastomosis and the proximal 

 portion of the right vitelline vein, form the portal vein, which gives off branches to 

 the hepatic sinusoids and connects with the left umbilical vein. For the develop- 

 ment of the portal vein, see Chapter IX. 



Transverse Sections of a Ten Mm. Pig Embryo 



Figures are shown of sections passing through the more important regions 

 and should be used for the identification of the organs. The level and plane of 

 each section is indicated by guide lines on Fig. 128. The student should compare 



Metencephalon 



Mesencephalon 



Gang, sii 

 Gang, and n. acccs 



Diencephafon 



Pulmonary artery -f -= 



Fig. 128. — Reconstruction of a 10 mm. pig embryo, showing tlie chief organs of the left side. The 

 numbered lines indicate the levels of transverse sections shown in the corresponding figures (129-143). 

 For the names of the various structures not lettered see Fig. 123. X 8. 



this with Figs. 118 and 123, and orient each section with reference to the embryo 

 as a whole. To avoid repetition most of the levels illustrated in the transverse 

 sections of the 6 mm. pig are not represented in the 10 mm. series. For this reason 



