THE ANATOMY OF TEN TO TWELVE MM. PIG EMBRYOS 



125 



The Veins. The cardinal veins have been reconstructed by Lewis in 

 a 12 mm. pig (Fig. 126). The veins of the head drain into the anterior 

 cardinal vein, which becomes the internal jugular vein of the adult. After 

 receiving the external jugular veins and the subdavian veins from the upper 



1.2 



1.3 



W.b. 



FIG. "1 26 B. Reconstruction of a 12 mm. pig embryo, to show the veins from the left side 

 (Lewis). X 9- A. .Umbilical artery; Ao., aorta; Au., right auricle (atrium); card.', card.", 

 superior and inferior sections of posterior cardinal vein; d, left common cardinal vein; D.C., 

 right common cardinal vein; D.V., ductus venosus; Jug.', Jug.", jugular -or ant. cardinal vein; 

 L., liver; L.s., anlage of lateral sinus; mx., transverse vein; P., pulmonary artery; Sc., subcardinal 

 vein; Scl., subclavian vein; sis., anlage of sup. longitudinal sinus; Um.d., right umbilical vein; 

 Ven., right ventricle; V.H.C., common hepatic vein; V.op., ophthalmic vein; V.P., portal vein; 

 -X", anastomosis between the right and left subcardinal veins. 



limb buds the anterior cardinals open into the common cardinal veins 

 (ducts of Cuvier). 



The posterior cardinal veins arise in the caudal region, course dorsal 

 to the mesonephroi, and drain the mesonephric sinusoids. The sub- 



