Frank A. Stromsten 461 



surface where it unites with a vein from the lesser curvature of the 

 stomach, the gastric vein, to form the portal vein of Bojanus. (Bo- 

 janus, Anatome Tesludinis EuropcFce. Tab. XXY, Fig. 128, sz.) 



The right abdominal vein passes through the right inferior lobe of 

 the liver and may open into portal vein of Bojanus, the mesenteric por- 

 tal, or, as in Fig. 1, into a large lateral branch of the latter. 



The portal vein of Bojanus (which in the a(hilt is really the direct 

 continuation of the left al)dominal vein) arises, as stated above, from 

 the union of the left abdominal with the much smaller gastric vein. It 

 passes directly across the body, from left to right, emljedded in a groove 

 on the ventral surface of the " isthmus "' of the liver, apparently increas- 

 ing very gradually in calil)re as it proceeds, and finally joins the mesen- 

 teric portal where the latter enters the liver. It receives during its 

 course a numl^er of tributaries from the duodenum, pancreas, and liver. 

 The largest of these branches comes from the dorsal region of tJie left 

 inferior lobe of the liver, and probably functions as the chief advehent 

 vein for that region. 



The mesenteric portal vein arises in the mesentery of the intestines 

 and enters the right half of the liver where it breaks up into the hepatic 

 venous network. The chief branches of the mesenteric portal are the 

 following veins : the descending colic, the ileo-colic, the intestinal, the 

 splenic, the posterior pancreatic, and the portal vein of Bojanus. Within 

 the liver it gives off a number of advehent branches, the largest of which 

 usually receives the right abdominal vein. 



Development of the Yeixs of the Hepatic Portal System in 



KiNOSTERXON PbNNSYLVAXICUM. 



The embryonic veins to be considered in this connection are : the 

 omphalo-mesenteric, or vitelline veins, and the umbilicals, or allantoic 

 veins. 



In the youngest stage studied (7.4 mm. crown-rump measurement 

 around the curvature of the body)," the anterior limbs are just beginning 

 to make their appearance as a low ridge involving several muscle seg- 

 ments on each side of the body. Tlie lungs are not yet indicated. The 

 liver is represented by a few tubules ventral to and on the right side of 

 the intestine. The first anlage of the pancreas has just been split off 

 as a simple tube from the doi"sal side of the flat mid-gut. The venous 

 system is represented by the following five pairs of veins: (1) the 



■■'All measurements were made in this manner. 



