THE FCETAL LIVER. 



781 



In the very yoimg foetus it occupies nearly the whole of the abdominal cavity ; 

 at the full period it still descends an inch and a half IdcIow 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, (]'<"■ — The foital liver is considerably thicker in proportion from 

 above downwards than that of the adult. It is generally of a darker hue. Its 

 consistence and specific gravity are both less than in the adult. 



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 fissm-e. and proceeds as 

 far as the transverse fissure. Here it divides into tn-o branches ; one of these, 

 the smaller of the two, continues onward in the same du'ection, and joins the 

 vena cava ; this is the ductus rciumix. 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 tnink of the umbilical vein) turns to the right 

 along the transverse or jjortal fissure, and ends in the vena portaj, which. })ro- 

 ceeding from the veins of the digestive organs, is in the foetus comparatively of 

 small dimensions. The umbilical vein, as it lies in the umbilical fissure, and 

 before it joins the vena porta3. gives off large lateral branches, which pass 

 dii-ectly into the right and left lobes of the liver. It also sends a few smaller 

 branches to the square lobe and to the lobe of Spigelius. 



Fig. 581. — Under Surface of the 

 FcETAL Liver, with its gre.\t 

 Blood-vessels, at the full 

 Period. 



a, the iimhilical A-ein, lying 

 in the umbilical fissure, and turn- 

 ing to the ri^dit side, at the 

 transverse fissure (o), to join the 

 vena portte (p) : the branch marked 

 d, named the ductus venosus, con- 

 tinues straight on to join the vena 

 cava inferior (c) : some branches of 

 the umliilical vein pass from a into 

 the substance of the liver ; >j. the 

 gall-bladder. 



Fig. r.8i. 



The blood which leaves the liver by the hepatic veins, and is carried into the 

 heart along with that of the vena cava inferior, consists of the following parts, 

 viz. ; 1. That of the mnbilical vein, which passes on directly by the ductus 

 venosus ; 2, that portion of the blood which is distributed to the liver by branches 

 proceeding immediately from the trunk of the umbilical vein ; and 3, the blood 

 from the digestive organs of the foetus arriving by the vena porta3. 



After birth the umbilical vein becomes obliterated from the umbilicus up to 

 the point of its giving off branches to the liver. The ductus venosus is also 

 obliterated, but the veins which were given as l^ranches from the umbilical 

 vein to the liver remain in communication with and appear as branches of the 

 left division of the portal vein. 



The Pancreas. — Tliis organ takes its origin in a mass of meso- 

 blastic tissue, which thickens the wall of the duodenum close to the 

 place where the rudiment of the liver is first seen, but placed more to 

 the left side. This mass may be seen on the third day in the chick. 

 There is, however, also a diverticulum from the primary wall of the 

 intestine or hypoblast. The same doubt prevails, as in regard to the 



