CH. LIX.] 



FORMATION OF THE VEINS 



853 



Wolffian bodies, and the hind limbs. 5. The ducts of Cuvier, each of 

 which receives a primitive jugular and a cardinal vein, and ends in the 



FIG. 648. Diagram representing an 

 anterior view of the primitive 

 heart, aortic arches, and their 

 roots. 1, Bulbus arteriosus ; 2, 

 ventricle ; 3, auricle ; 4, sinus 

 venosus ; 5, descending aorta ; 6, 

 omphalo-mesenteric vein ; 7, um- 

 bilical vein ; 8, duct of Cuvier ; 



9, dorsal roots of aortic arches ; 



10, ventral roots of aortic arches. 



FIG. 649. Diagram representing a side view of the 

 primitive heart with the cephalic aortic arches 

 and their roots. 1, First cephalic aortic arch ; 2, 

 second cephalic aortic arch ; 8, third cephalic 

 aortic arch ; 4, fourth cephalic aortic arch ; 5, 

 fifth cephalic aortic arch ; 6, bulbus arteriosus ; 

 7, ventricle ; 8, auricle ; 9, sinus venosus ; 10, 

 omphalo-mesenteric vein (left) ; 11, ventral roots 

 of aortic arches ; 12, dorsal roots of aortic arches ; 

 13, descending aorta. 



auricle. Thus six veins terminate in the sinus venosus, and through 

 it in the auricle (fig. 648). Both ducts of Cuvier retain their con- 



FIG. 650. Diagram representing a side view of 

 heart after it has folded on itself. 4, Ventral 

 root of fourth aortic arch ; 5, fifth aortic 

 arch ; 6, bulbus arteriosus ; 7, ventricle ; 8, 

 auricle ; 9, sinus venosus ; 10, left omphalo- 

 mesenteric vein. 



FIG. 651. Diagram representing 

 an anterior view of the heart 

 after it has folded on itself. 

 4, Ventral root of fourth 

 aortic arch ; 5, fifth aortic 

 arch ; 6, bulbus arteriosus ; 

 7, ventricle ; 8, auricle. 



nection with the auricle, the right forming the lower part of the 

 superior vena cava, and the left the oblique vein of Marshall in man, 

 and the lower part of the left superior cava in some mammals. 



