PECULIARITIES OF THE FCETUS. 275 



the influence of respiration, by having to pass unavoidably 

 through the lungs. 



SECT. II. OF THE PECULIARITIES OF THE CIRCULATION OF-T,HE 



FOETUS CONNECTED WITH ITS NOURISHMENT. 



The Umbilical Vein, one of the constituents of the umbilical 

 chord, brings the blood from the placenta to the foetus. This 

 vessel is from three to four lines in diameter, and enters at the 

 navel; thence it goes along the loose margin of the suspensory 

 ligament of the liver, and traverses the anterior half of the um- 

 bilical fissure, to terminate in the left branch of the sinus of the 

 vena portarum. In this course through the liver, the umbilical 

 vein sends off to the right and the left lobe several small branches. 

 As the intestinal circulation of the foetus is too small to send 

 much blood through the vena portarum, it would be sufficiently 

 correct to consider the sinus venae portarum as the bifurcation 

 of the umbilical vein; but, as this might introduce a confusion 

 into the description, it will be better to retain the adult nomen- 

 clature. 



The Ductus Venosus is a vein which occupies the posterior 

 half of the umbilical fissure, and is about a line and a half in 

 diameter. It arises from the left branch of the sinus portarum, 

 opposite to the place where the umbilical vein entered or termi- 

 nated, and is consequently in the same line with the latter. Tra- 

 versing the posterior part of the umbilical fissure, it terminates 

 in the left vena cava hepatica, as this vein is about joining the 

 ascending cava, just below the tendinous centre of thediaphragm. 

 Through this route much of the blood of the umbilical vein is 

 carried directly to the right auricle of the heart, and then passed 

 through the foramen ovale into the left auricle by the mechanism 

 of the Eustachian valve. 



From these considerations, it is evident that the umbilical 

 vein really performs the office of a vein till it reaches the liver, 

 but that there much of its blood is spent through the portal 

 circulation, upon the structure of this viscus, and that what re- 

 mains is carried through the ductus venosus to the heart Like 



