TRANSVERSE SECTIONS <)[ A TEX MM. PIG EMBRYO 



127 



fused with the right, courses from the yolk sac cephalad of the intestinal 

 loop. Near a dorsal anastomosis 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, forms the portal vein, which gives off branches to the hepatic sinu- 

 soids and connects with the left umbilical vein. For the development 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; these 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 this with Figs. 118 and 123, and orient each 



Myelencephalon 

 Gang. sup. n. g 

 Gang, and n. access. 



Metencephalon 



Mcsencephalon 



Diencephalon 



ton 



Pulmonary artery 



.129 



-Telencephalt 



-130 

 131 

 2 Olfactory pit 



t 



137 

 138 

 '39 

 140 



FIG. 128. Reconstruction of a 10 mm. pig embryo, showing the 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. 



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, the former series 

 will be found very instructive in supplementing the following descriptions. 



