422 FISHES. 



and from this it is driven through a contractile conus arteri- 

 osus, with three longitudinal rows of five valves, into the 

 ventral aorta. 



The ventral aorta gives off a pair of posterior innominate 

 arteries, which take blood to the three posterior gills, and a 

 ))air of anterior innominate arteries which supply the anterior 

 gill and the hyoid half gill on each side. 



The purified blood passes from each half gill by an 

 eierent branchial artery. To begin with there are nine 

 of these on each side, but by union they are reduced 

 to three efferent trunks which combine to form the dorsal 

 aorta. 



From tfe efferent branchial of the hyoid arch, a carotid 

 arises, which divides into internal and external branches 

 supplying the brain and head. From the first of the 

 efferent trunks, a vertebral arises which supplies the brain 

 and spinal cord. 



The dorsal aorta gives off — (i) two brachials to the 

 pectoral fins ; (2) a coeliac to the stomach, duodenum, and 

 liver ; (3) a superior mesenteric to the intestine, pancreas, 

 and spleen ; (4) spermatic arteries to the reproductive 

 organs ; (5) an inferior mesenteric to the rectum ; (6) renal 

 arteries to the kidneys ; (7) arteries to the pelvic fins. It 

 ends in the caudal artery. 



At each end of the bow-shaped sinus venosus, there is 

 a pre-caval sinus. This receives venous blood as follows : 

 — {a) from the head by a jugular vein, (b) from the liver 

 by a hepatic sinus, which runs from one pre-caval sinus 

 to. the other like the string of the bow, {c) from a large 

 posterior cardinal sinus (between the reproductive organs) 

 by a cardinal vein on each side, {d) from the hind-fin 

 by an epigastric, with which a brachial from the fore-limb 

 unites anteriorly. The great cardinal sinus receives blood 

 from the hind-limbs, the kidneys, and other posterior 

 parts. 



Blood passes into the liver {a) from the cceliac artery, and 

 {b) by portal veins from the intestine (the hepatic portal 

 system) ; blood leaves the liver by hepatic veins which enter 

 the hepatic sinus. 



Blood passes into the kidneys (a) from the renal arteries, 

 and (b) by renal portal veins from the caudal, pelvic, and 



