872 A MANUAL OF PHYSIOLOGY 



route of .the ductus venosus, and empties itself directly into the inferior 

 vena cava. The latter gathers up the more or less vitiated blood from 

 the inferior extremities and the renal and hepatic veins, and pours 

 its mixed but still fairly oxygenated contents into the right auricle. 

 By means of the Eustachian valve, the jet coming from the mouth of 

 the inferior vena cava is directed into the left auricle through the 

 foramen ovale in the inter-auricular septum. There it is joined 

 by the trickle of blood which is creeping through the unexpanded 

 lungs. The left ventricle propels its contents through the aorta, 



The arrow is in 



the Foramen Ovale 



Right Auricle 



Right Ventricle ^^BK^S9lllMHf^iB LllP S s 



Pulmonary Artery 



. - . ,,.. ^-v~,^^mM^ z Aorta 



Inf. Vena Cava \ ' iy;;v /,; J v ,#Mffl /'/ &Ji Ductus Arteriosus 



Inf. Vena Cava 



Ductus Venoius 



Liver 



Portal Vein ^^^^^^^^^ ^^^ 



^^^^_n_ " " Kidney 



Intestine 



Umbilical A tery 



"""-""" '' "' ' *" ~ " Umbilical Vein 



FlG. 336.- DIAGRAM OF THE SECOND CIRCULATION IN THE FCETUS. 

 The arrows show the direction of the blood-flow. 



and thus a b-rge part of this comparatively pure or second-best 

 blood is sent to the head and upper extiemities. It returns in 

 a vitiated state* oy the superior vena cava into the right auricle, and 

 owing to the position of the Eustachian valve and the direction of 

 the current, it i'ows now not through the foramen ovale, but into the 

 right ventricle. Thence it is driven through the pulmonary artery, 

 but only a small quantity of it finds its way through the lungs ; the 

 main stream is ^nort-circuited through the ductus arteriosus, and 

 mingles with the contents of the thoracic aorta below the origin of 

 the cephalic and brachial vessels. 



