300 



STUDY OF PIG EMBRYOS. 



much smaller, and runs only a short distance downward from the geniculate gan- 

 glion and is entirely separate from the motor portion. The morphological constitu- 

 tion of the facial nerve is still very obscure, and a satisfactory account of its 

 development is, for the present, impossible. 



Section through the Vena Cava Inferior (Fig. 206). The section displays the 

 huge vena cava inferior cut through most of its length. For the composition of 



Ao.n 



Ao.S 



P.A. 



V.s.c. 



'Ao 



FIG. 206. PIG of 12.0 MM. FRONTAL SERIES 6, SECTION 423. 



Ao, Main dorsal aorta. Ao.D, Right descending aorta. Ao.S, Left descending aorta. Au.D, Right auricle. 

 Au.S, Left auricle, c, Vena cava passing through the caval ligament. Nch, Notochord. Om.min, Omentum 

 minus. P.A, Pulmonary aorta. Sp.e, Spinal cord. St, Stomach. S.V, Sinus venosus. V.C.I, Vena cava 

 inferior. V.E, Valvula Eustachii. V.S. Valvula sinistra. V.s.c, Vena subcardinalis. W.B, Wolffian body. 

 X 15 diams. 



the vein see page 257. In the section it starts between the Wolffian bodies, W.B, as 

 a large vessel, V.C.I, formed by the median union of the two subcardinal veins 

 of the Wolffian bodies. It passes upward, c, through a thin band of tissue, the 

 caval ligament, to the right of the lesser omentum, Om.min, into the substance of 

 the liver, Li, through which it takes a slightly sinuous course. Several junctions 



