151 



DEVELOPMENT OF THE PRINCIPAL VEINS, 



The left duct of Cuvier is obliterated. But even in the adult, traces of this vessel 

 can always be recognised in the form of a fibrous band, or sometimes a narrow vein, 



Fig. 186. A and B. DIAGRAMMATIC OUTLINES OP THE VESTIGE OF THE LEFT SUPERIOR CAVA AND OF 

 A CASE OF ITS PERSISTENCE. (Sketched after Marshall. ) |. 



The views are supposed to be from before, the parts of the heart being removed or seen through. 



1, 1', internal jugular veins ; 2, 2', subclavian veins ; 3, right innominate ; 3', right or regular 

 superior cava ; 4, left innominate, normal in A, rudimentary in B ; 5, in A, the opening of the superior 

 intercostal vein into the innominate ; 5', vestige of the left superior cava or duct of Cuvier ; 5, 5', in B, 

 the left vena cava superior abnormally persistent ; 6, coronary sinus ; 6', coronary veins ; 7, superior 

 intercostal trunk of the left side (left cardinal vein) ; 8, the principal azygos (right cardinal vein) ; 

 7', 8', some of the upper intercostal veins ; 9, the opening of the inferior vena cava, with the Eustachian 

 valve. 



which descends obliquely over the left auricle ; and in front of the root of the left 

 lung there remains an indication of its former presence in the form of a small fold 



Fig. 187. VIEW OF THE FOETAL HEART AND GREAT 



VESSELS, FROM THE LEFT SIDE, TO SHOW THE VESTIGE 

 OF THE LEFT SUPERIOR VENA CAVA IN SITU. (This 



figure is planned after one of Marshall's.) 



a, right auricle ; b, left auricle and pulmonary veins ; 

 c, the conus arteriosus of the right ventricle ; d, the left 

 ventricle ; e, descending aorta ; + , vestigial fold of the 

 pericardium ; /, arch of the aorta, with a part of the 

 pericardium remaining above ; g. main pulmonary artery 

 and ductus arteriosus; g', left pulmonary artery ; 1,1', 

 right and left internal jugular veins ; 2, 2', subclavian 

 veins ; 3, 3', right innominate and superior vena cava ; 

 4, left innominate ; 5, 5', remains of the left superior 

 cava and duct of Cuvier, passing at + in the vestigial 

 fold of the pericardium, joining the coronary sinus, 6, 

 below, and receiving above the superior intercostal vein, 

 7 ; 7', 7', the upper and lower intercostal vein. 



of the serous membrane of the pericardium, the vestigial fold of Marshall, to whom 

 is due the first full elucidation of the nature and relations of the left primitive vena 

 cava superior. 



The left duct of Cuvier has been observed persistent as a small vessel in the 

 adult. Less frequently a right and a left innominate vein open separately into the 



