234 



PISCES 



hearts of all fishes except the Dipnoans contain venous blood only. 

 The ventricle forces the blood through the ventral aorta to the 

 afferent branchial arteries to the capillaries of the gills, where it 

 is oxygenated and thence passes into the efferent branchial arteries 

 and into the dorsal aorta, thence throughout the body. 



Juqu/or vein 

 Inferior Jutjular vein 



Veins from abdominal woll- 

 Cordinal vein — I 



Hemorrhoidal vein — -1 



Ppigosfric vein —■ 



Iliohemorriioidal vein- 

 Posterior anastomosis_ 

 of cardinal vein 



Femoral vein~~-^—r — 



Bulbus arteriosus 



-Con us arteriosus 



/Auricle 



■Sinus venosus 



Ventricle 



frecavol sinus 



Hepatio sinus 

 ■ Cardinal vein 



-Brachial vein 



Cardinal sinus 

 Spermatic sinus 



Henal portal veiry 



^Factors of renaj portal 

 vein from pelvic and 

 lumbar regions 



^Branches of renal portal 

 vein enterincj l^idney 



Caudal vein 



Fig. III. Venous circulation of skate. (After Parker's Zootomy. Courtesy of Mac- 



millan and Co., Ltd.) 



The renal portal system is well developed in the Elasmobranchs 

 but disappears in birds and mammals. In the skate the caudal vein 

 brings blood from the tail, dividing in the abdominal cavity to form 

 the right and left renal portal veins, which end in afferent renal veins 

 supplying the kidneys. The blood leaves the kidneys by the 

 posterior cardinal veins which enter the cardinal sinus. 



The hepatic portal vein is formed by the union of veins that bring 

 blood from the stomach, intestine, spleen and pancreas. The 

 large vessel thus formed passes forwards and enters the liver. Leav- 



