THE ANATOMY OF A SIX MM. PIG EMBRYO 



lOI 



rate and run lateral to the umbilical arteries. The left vein is much the larger. 

 Both, after receiving branches from the posterior limb buds and from the body 

 wall, pass cephalad in the somatopleure at each side (Fig. 72). Their course is 

 first cephalad, then dorsad, until they enter the liver. The left vein enters a wide 

 channel, the ductus venosus, which carries its blood through the hver, thence to 

 the heart by way of the right vitelline trunk. The right vein joins a large sinu- 

 soidal continuation of the portal vein in the liver. This common trunk drains 

 into the ductus venosus. 



Spiiiii 

 Anterior cardiiiu, 

 Cervical 



Pericardial i 



R. common cardinal va 



Post, cardhial vci 



Esopha 



Large venous sinusoid livrr 



Anterior limb bud 



In}, vena cava 



Post, cardinal vein 



Mesonephros {cut surface)' 



R. subcardinal 



Venous sinusoid on dorsum 

 mesonephros 



Dorsal 

 Notochor 



clica 



mnion 

 ■dinal vein 



lomach {cut edge) 

 Omental bursa 

 Mciogastrium 



Mesonephros {cut surface) 



'apillary anastomosis between 



subcardinal veins 

 I 'ilelline artery in dorsal 



mesentery 

 Capillary anastomosis between 



subcardinal veins 



eiwus sinusoid on dorsum of 

 mesonephros 



cord 



Fig. 103. — Reconstruction of the cardinal and subcardinal veins of a 6 mm. pig embryo showing the 

 early development of the inferior vena cava (K. L. Vehe). X 22. In the small orientation figure (cf. 

 Fig. 105) the various planes are indicated by broken lines — * *. 



The anterior cardinal veins (Figs. 103 and 104) are formed to drain the plexus 

 of veins on each side of the head. These vessels extend caudad and lie lateral to 

 the ventral portion of the myelencephalon. Each anterior cardinal vein receives 

 branches from the sides of the myelencephalon, then curves ventrad, is joined by 

 the linguo-facial vein from the branchial arches and at once unites with the pos- 

 terior cardinal of the same side to form the common cardinal vein. This, as we 

 have seen, opens into the sinus venosus. 



