CIRCULATORY SYSTEM 



789 



vessel known as the ductus arteriosus or the duct of Botallus (Fig. 345, 

 C, d, b) in some of the urodeles. In some of the higher vertebrates one 

 occasionally finds a vestige of this persisting also, otherwise it entirely 

 disappears. 



The ductus Botalli is quite important in the embryonic circulation 

 of amniotes, because the greater part of the blood goes through it to 

 reach the dorsal aorta during the time the allantois is the organ of res- 

 piration, while only enough blood goes through the pulmonary artery 

 to nourish the lung. The duct closes with the first inspiration of air, 

 while all blood passing into the last arch goes to the lung. 



In the lung fishes and amphibia where there is but a single ventricle 

 in the heart, the pulmonary arteries are connected with the ventral aorta 

 just as are the other aortic arches. In higher forms, however, such as 

 the amniotes, where there is either a partial or complete division of the 



Fig. 449. 



777. 



Schematic diagrams of circulatory systems in I, Petromyzon, II, Teleosts, HI, 

 in the higher vertebrates. I to VIII, gill arches ; A, dorsal aorta ; A, atrium ; Ab, 

 gill veins ; Acd, caudal artery ; All, allantoic artery ; Am, omphalo-mesenteric 

 artery; RA, and rad.ao., Aortic radices (roots of the aorta) ; S. S 1 , two branches 

 card., anterior arid posterior cardinal veins ; car. ex., c, and car. int., c' external 

 and internal carotid arteries ; coel.mes., coeliaco-mesenteric artery ; duct.cuv., and 

 D, duct of Cuvier ; E, external iliac artery ; H C, posterior cardinal vein ; Ic, 

 common iliac artery ; hy.v., gill veins of the hyoid arch ; k.art., gill arteries ; 

 k.ven., gill veins ; KL., gill clefts ; ophth, ophthalmic artery ; orb.nas., orbito-nasal 

 artery; RA, and rad.ao., Aortic radices (roots of the aorta) ; S. S 1 , two branches 

 of the gill veins which pass into the aortic radices ; Sb, Sb, and subl., subclavian 

 artery ; Sb 1 , subclavian vein ; si, and sin.ven., sinus venosus ; spr.k., spiracle gill ; 

 v, and ventr., ventricle ; VC, anterior cardinal vein ; Vm, omphalo-mesenteric vein. 

 (From Schimkewitsch, I, after Vogt, Jung and Bridge; II, Parker, III, Wieders- 

 heim.) 



