568 THE UMBILICAL CORD. 



minute, that they are woven, as it were, like the most delicate 

 threads, into the tissues of the veins, or rather in some obscure 

 manner insinuate themselves into them ; hence they almost 

 entirely elude the sight. But all the veins, by a retrograde 

 movement, unite their twigs and terminate in one trunk like 

 the branches of a tree, in the same manner as the mesenteric 

 veins, all of which terminate in the vena portse. 



Near the embryo [the umbilical veins] are divided into two 

 trunks, but when entered within it they constitute one um- 

 bilical vein, which ends in the vena cava, near the right auricle 

 of the heart, and passes through the liver, entering the vena 

 portse ; giving off no branches besides until it leaves the con- 

 vex portion of the liver by a very large orifice. So that if the 

 vena cava is opened from the right auricle downwards and 

 emptied of blood, three apertures may be seen close to each 

 other; one is the entrance of the vena cava descendens, the 

 second that of the hepatic vein, which ramifies throughout the 

 convex portion of the liver, and the third is the origin of the 

 umbilical vein. Hence it is quite clear that the origin of the 

 veins is by no means to be looked for in the liver ; inasmuch 

 as the orifice of the vena cava descendens is much larger than 

 the hepatic branch, which is indeed equalled in size by the um- 

 bilical vein. For the branches are not said to be the origin of 

 their trunk ; but where the trunk is greatest there the origin 

 of the veins is to be looked for, and this is the case at the 

 entrance of the right ventricle : here, then, the origin of all 

 veins, and the storehouse of the blood must be placed. 



To return to the umbilical vessels, which are not subdivided 

 in the same way in all animals; for in some two or more 

 branches of veins are found within the body of the foetus, 

 some of which pass through the liver, whilst others join the 

 portal and mesenteric veins. In the human foetus, at a dis- 

 tance of three or four fingers' breadth from the umbilicus, the 

 trunks of the arteries and veins are involved together in a 

 complicated manner, (as if one were to twist several waxen 

 tapers in the form of a stick,) and are besides covered and held 

 together by a thick gelatinous membrane. This cord passes 

 on towards the chorion, and w T hen arrived at the concave por- 

 tion of the placenta and the inner surface of the chorion, splits 

 into innumerable branches; these divide again, and constitute 



