880 THE LIVER. 



the full period it still descends an inch and a half below the margin of the thorax, 

 overlaps the spleen on the left side, and reaches nearly down to the crest of the ilium 

 on the right. 



Form, Colour, &c. The foetal liver is considerably thicker from above down- 

 wards than that of the adult. It is generally of a darker hue. Its consistence and 

 specific gravity are both less than in the adult. 



Blood- Vessels. The blood-vessels of the fcetal liver present several important pecu- 

 liarities, with which, indeed, those previously mentioned are more or less connected. 

 Up to the moment of birth, the greater part of the blood returned from the placenta 

 by the umbilical vein passes through the liver of the foetus before it reaches the 

 heart ; while a smaller part is transmitted more directly to the right auricle. 

 During foetal life, the umbilical vein runs from the umbilicus along the free margin 

 of the suspensory ligament towards the anterior border and under surface of the 

 liver, beneath which it is lodged in the umbilical fissure, and proceeds as far as 

 the transverse fissure. Here it divides into two branches ; one of these, the smaller 

 of the two, continues onward in the same direction, and joins the vena cava; this 

 is the ductus venosus, which occupies the posterior part of the longitudinal fissure, 

 and gives to it the name of the fossa of the ductus venosus. The other and larger 

 branch (the trunk of the umbilical vein) turns to the right along the transverse or 

 portal fissure, and ends in the vena portse, which, in as much as it proceeds from the 

 veins of the digestive organs, is in the foetus comparatively of small dimension*. 

 Moreover, the umbilical vein, as it lies in the umbilical fissure, and before it joins the 

 vena portae, gives off some lateral branches, which enter the left lobe of the liver. 

 It also sends a few branches to the square lobe and to the lobe of Spigelius. 



Fig. 617. Fig. 617. UNDER SURFACE OF THE 



F(ETAL LlVER, WITH ITS GREAT 

 BLOOD-VESSELS, AT THE FULL 



PERtOD. f 



The rounded outline of the organ, 

 and the comparatively small differ- 

 ence of size between its two lobes, 

 are seen : a, the umbilical vein, 

 lying in the umbilical fissure, and 

 turning to the right side at the 

 transverse fissure (o), to join the 

 vena portse (p) : the branch marked 

 d, named the ductus venosus, con- 

 tinues straight on to join the vena 

 cava inferior (c) : a few branches of 

 the umbilical vein enter the sub- 

 stance of the liver at once ; g, the 

 gall-bladder. 



The blood of the umbilical vein may therefore be considered as reaching the 

 ascending vena cava in three portions. Some is carried into it by the more direct 

 passage of the ductus venosus ; another, the principal portion, passes first through 

 the portal veins, and then through the hepatic veins ; whilst a third portion, supplied 

 by direct branches to the liver, is also returned to the cava by the hepatic veins. 



Changes after birth. Immediately after birth, at the cessation of the current 

 which previously passed through the umbilical vein, and on the establishment of an 

 increased circulation through the lungs, the supply of blood to the liver is diminished 

 by nearly two-thirds. The umbilical vein and ductus venosus become empty and con- 

 tracted, and soon afterwards they begin to be obliterated, and are ultimately converted 

 into the fibrous cords already described, that one which represents the umbilical vein 

 constituting the round ligament of the liver. At the end of six days the ductus 

 venosus has been found to be closed ; but it sometimes continues open for several 

 weeks. That portion of the umbilical vein which supplied direct branches to the 

 liver remains open, though diminished in size, and, being in communication with 

 the leffc branch of the vena portse, continues afterwards to transmit blood to a part of 

 the liver from that vessel. 



Concurrently with, and doubtless in some measure dependent on ; the sudden 



