THE VASCULAR SYSTEM 239 



genetic history has been investigated by Choronshitzky (1900), who 

 showed that it is really the persisting left vitelline vein of the embryo. 

 It is therefore homologous with the V. subintestinalis of the fish. 

 According to this author the right vitelline vein is never large and 

 disappears early. Hochstetter (1908) confirms these views. 



{£) The anterior gastric vein.^ It would perhaps seem more correct 

 to regard this vessel as a branch of the portal vein than as 2. factor^ but 

 actually it is both. It passes along the dorsal surface of the liver and 

 has the appearance of being the direct continuation of the abdominal 

 vein. On the one side it sends numerous branches into the liver, and 

 on the other it receives four or five factors from the ventral stomach- 

 wall. These factors are always associated with corresponding arteries, 

 and there is usually an artery on either side of the venous factor. 



It should be noted that the blood-system of the stomach is of a two- 

 fold nature. It both receives its blood from, and returns it into, 

 distinct vessels on both dorsal and ventral sides. 



The Renal Portal System (PI. XVI). 



A. The F. caudalis (v.cd.), as its name implies, arises near the 

 extremity of the tail and runs forwards through the haemal arches ven- 

 tral to the caudal artery. Almost immediately after it emerges from 

 the haemal canal it divides symmetrically into two vessels, which pass 

 respectively to the dorso-lateral border of each kidney. These veins 

 are portal to the kidneys. Hochstetter's name for them is retained, 

 namely, Jacobson's veins. 



VV. Jacobsoni (v.J.) (Hochstetter). Each Jacobson's vein, al- 

 most immediately after its origin from the caudal vein, receives a 

 small inguinal vein from the muscles of the inguinal region, and then 

 passes to the dorso-lateral surface of the kidney, to which organ it 

 gives a number of Venae advehentes. Just before reaching the level 

 of the iliac artery Jacobson's vein bends round the edge of the kidney 

 to the ventral side, passes ventral to the artery, and immediately 

 anterior to it anastomoses with the common iliac vein. Jacobson's 

 vein, thus reinforced, passes anteriorly along the lateral border of 

 the kidney, giving off on the one side numerous Fenae advehentes 

 to the kidney, and receiving on the other four or five dorso-lumbar 

 veins from the muscles of the back, and also a number of posterior 



' This terminology is due to O'Donoghue (1921). Beddard (1905) regards it as the 

 anterior continuation of the abdominal vein. As O'Donoghue rightly points out, only a 

 study of its development can decide to w^hich it belongs. Reference should be made to 

 O'Donoghue's paper. 



