440 THE DOGFISH chap. 



into a pair of cardinal veins {crd. v) which pass forwards, 

 become swollen to form sinuses (Fig. 113, /. card, s, r. card, s), 

 receive veins from the reproductive organs, muscles, &c., and 

 finally enter the precaval sinus. 



From the stomach, intestine, spleen, and pancreas the 

 blood is collected by numerous veins, which all join to form 

 a large hepatic portal vein ((Fig. no, h. p. v, Fig. 113, 

 k. port. v). This behaves in the .same way as the renal 

 portal : instead of joining a larger vein on its way to the 

 heart, it passes to the liver and breaks up to connect with 

 the capillaries of that organ ; its blood, deprived of oxygen 

 but loaded with nutrient matters from the enteric canal, 

 mingling with the oxygenated blood brought to the liver by 

 a branch of the cceliac artery. After circulating through 

 the capillaries of the liver the ■blood is taken by a pair of 

 hepatic sinuses (h. v, hep. s) to the sinus venosus. 



The course and arrangement of the veins, like that of the arteries, is 

 very similar to that existing in the tadpole, in which several important 

 changes occur at metamorphosis. With the disappearance of the tail 

 and caudal vein, the renal portal veins receive their blood from the 

 hind-limbs only. The hinder parts of the two cardinal veins, situated 

 between the kidneys, fuse into one, and their anterior parts disappear, 

 a new vessel being developed which conducts the blood from the fused 

 cardinals to the sinus venosus : the whole of the great vein thus 

 formed is the posl(aval (p. 82, fig. 21), which is present in all 

 Vertebrates above the fishes. 



The iliac veins of the dogfish (Fig. no, //. v) pour the 

 blood from the pelvic fins into \\\ii lateral veins l^'xg?,. no 

 and 113, lat. v) — paired trunks running forwards in the side 

 walls of the body to the sinus venosus, and receiving at 

 their anterior ends the subclavian veins (scl. v) from the 

 pectoral fins. In addition to the dorsally situated jugular 

 veins, there are paired inferior Jugulars (Fig. 113, inf. jug. v), 



