456 THE DOGFISH CHAP. 



the kidneys the blood is returned into a pair of partially 

 united cardinal veins (crd. v] which pass forwards, become 

 swollen to form large sinuses anteriorly (Fig. 122, card], 

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

 and finally each communicates with a precaval sinus 

 (pr. cv), which passes vertically downwards and enters 

 the sinus venosus. 



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. 119, h.p. 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 veins (li.v) , which enlarge to form a large sinus (h.s) , 

 and this opens into the sinus venosus (compare p. 85). 



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 postcaval (p. 82, Fig. 21), which 

 is present in the Dipnoi (p. 430) and in all Vertebrates above 

 the fishes. 



The iliac veins of the dogfish (Fig. 119, il) pour the 

 blood from the pelvic fins into the lateral veins (Figs, in, 

 119, and 122, lat] paired trunks running forwards in 

 the side walls of the body to the sinus venosus, and 

 communicating at their anterior ends with the stibclavian 



