THE FCETAL CIRCULATIOX. FORAMEN OVALE. 



i99 



obliquely on the left auricle ; and in front of tlie root of the left lung there 

 remains a small fold of the serous membrane of the iiericardium, the re.sfii/ial 

 fold of the pericardium, so named by Marshall, to whom is due the first full 

 elucidation of the natui'e and relations of the left primitive vena cava. 



The left duct of Cu%'ier has been observed persistent as a small vessel in the 

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

 the right am'icle. an arrangement which is also met witli in birds and in certain 

 mammals, and which results from the vessels of the left side being developed 

 similarly to those of the right, while the cross branch remains small or absent. 

 (Quain on the Arteries, plate 58, figs. 9 and 10.) 



Fig. 596. — View op the F<etal Heart 

 AND Great Vessels, from the left 



SIDE, TO SHOW THE VeSTIGE OF THE 



Left Superior Cava VEI^f in situ. 

 (This figure is j)lanned after one of 

 Marshall's, and slightly altered accord- 

 ing to an original dissection.) 



a, right auricle ; b, left auricle and 

 pulmonary veins ; c, the conns arteriosus 

 of the right ventricle ; d, the left ven- 

 tricle ; c, descending aorta ; + , vestigial 

 fold of the loericardium ; /, arch of the 

 aorta, with a part of the pericardium 

 remaining superiorly ; r/, main pulmonary 

 artery and ductus arteriosus ; [/', left pul- 

 monary artery ; 1,1', right and left in- 

 ternal jugular veins ; 2, 2', subclavian 

 veins ; 3, 3', right innominate and superior 

 vena cava ; 4, left innominate or com- 

 municating vein ; 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, joining into one. 



A case is recorded by Gruber, in which the left vena azygos opened into the 

 coronary sinus, and was met by a small vein descending from the union of the 

 subclavian and jugular. (Reichert and Dubois. RejTnond's Archiv, 18(54, p. 729.) 

 In this case, the jugular veins had been developed in the usual manner, while 

 the left vena azygos continued to pour its blood into the duct of Cuvier. 



(Consult KoUiker, Entwickelungsgeschichte, p. 41-1, et seq. ; J. Marshall on 

 the Development of the great Anterior Veins in Man and Mammalia, in Phil. 

 Trans., part i., 1850 ; and Wenzel Gruber, Uber die Sinus Communis und die 

 Valvulaj der Vense Cardiaca3, &c., in Mem. de I'Acad. imper. des Scien. de St. 

 Petersbourg, 1SG4 ; and in Virchow's Archiv, Jan. 1SG6.) 



PECULIARITIES OP THE FCETAL ORGANS OP CIRCULATION. 



It may be useful here to recapitulate shortly the peculiarities of 

 structure existing in the advanced stage of the formation of the foetal 

 organs of circulation with reference to their influence in determining 

 the course of the blood during intra-uterine life, and the changes which 

 occur in them in consequence of the establishment of pulmonary respi- 

 ration at birth. 



The so-called foramen ovale retains the form of a free oval opening 

 in the septum auricularum up to the fourth month, but in the course o"f 

 that month and tlie next there takes place the growth from below and 

 on the left side of a flat plate or curtain, which advancing upwards fills 

 up the floor of the fossa ovalis, adheres to its left borders as far as its 

 anterior part, and then becoming free and passing beyond the anterior 



