FOETAL CIRCULATION. 437 



to the fo3tal tufts of the placenta, do not exist in the adult. 

 The ductus venosus, which conveys a portion of the blood of 

 the umbilical vein to the vena cava ascendens, and the um- 

 bilical vein itself do not exist in the adult. 



The Eustachian valve, situated at the inner margin of the 

 vena cava ascendens as it opens into the right auricle, does 

 not exist in the adult. The foramen ovale, or the opening 

 between the right and the left auricle, through which the 

 blood from the vena cava ascendens is directed into the left 

 auricle, does not exist in the adult. The ductus arteriosus, 

 which conveys the blood from the left pulmonary artery to 

 the arch of the aorta, does not exist in the adult. In the 

 adult, the pulmonary arteries receive all the blood from the 

 right ventricle. In the foetus, the pulmonary arteries receive 

 a small quantity of blood, as compared with that which passes 

 to the aorta through the ductus arteriosus. 



Keeping in view these peculiarities of the circulatory ap- 

 paratus, the entire course of the blood, during foetal life, is 

 as follows : 



Beginning with the abdominal aorta, we follow the course 

 of blood into the two primitive iliacs, and thence into the 

 internal iliacs. From the two internal iliacs, the two hypo- 

 gastric arteries arise, which ascend along the sides of the 

 bladder to its fundus, thence pass to the umbilicus, and go to 

 the placenta, forming the two umbilical arteries. In this 

 w^ay, the blood of the foetus goes to the placenta. 



The umbilical vein enters the body of the foetus at the. 

 umbilicus ; passes along the margin of the suspensory liga- 

 ment to the under surface of the liver ; gives off one branch 

 of large size, and one or two smaller branches to the left lobe ; 

 a branch each to the lobus quadratus and the lobus Spigelii ; 

 and the vessel reaches the transverse fissure. At the trans- 

 verse fissure, it divides into two branches, the larger of which 

 joins the portal vein and enters the liver ; and the smaller, 

 which is the ductus venosus, passes to the vena cava ascendens, 

 at the point where it receives the left hepatic vein. Thus, the 



