476 SANGUIFEROUS SYSTEM. 



the bodies of the dorsal vertebrae, to form the abdominal 

 aorta, which continues its course backwards along the median 

 plane, beneath the vertebrae, to the coccygeal region, where 

 it becomes enclosed during the rest of its course, by the 

 inferior converging laminae of the coccygeal vertebrse. 



The great coeliac artery which supplies most of the abdo- 

 minal viscera, arises from the commencement of the aortal 

 trunk formed by the union of the branchial veins, and sends 

 oif numerous branches, which ramify extensively on the sto- 

 mach and intestines, on the liver, the spleen, the air-sac, 

 and the genital organs. From the principal trunk of the 

 aorta, within the cavity of the abdomen, and behind the 

 great visceral artery, several lateral branches come off at 

 regular distances, one pair for each vertebra, which supply 

 the contiguous muscular, osseous and cutaneous parts, and 

 send down branches as renal arteries to the long, narrow, 

 lobulated kidneys, extended along the sides of the vertebral 

 column. The brachial arteries, for the pectoral fins, origi- 

 nate from the aorta near its commencement, and two femoral 

 arteries likewise come off from the aorta in the region of the 

 pelvis, for the ventral fins. The coeliac artery sometimes 

 originates from the common trunk of the right branchial 

 veins before it unites with the left to constitute the aorta. 

 The posterior continuation of the aorta extends single along 

 the inferior ring of the coccygeal vertebrae, above the venous 

 trunk which occupies the same canal, and it sends off regular 

 pairs of intervertebral branches which pass upwards and 

 downwards on each side, to supply the muscular and other 

 parts of the tail. 



The venous blood collected from the lower and posterior 

 coccygeal region of fishes, is received by numerous pairs of 

 lateral branches, which convey it into the inferior caudal 

 vein, enclosed in the lower rings of the coccygeal vertebrae. 

 This inferior caudal vein lies below the great arterial trunk, 

 enclosed in the same inferior vertebral rings, and conveys the 

 venous blood from the cutaneous and muscular parts of the 

 tail forwards to the abdomen. It forms the commencement 

 of the great posterior vena cava, it continues its course along 

 the abdomen, under the bodies of the dorsal vertebrae, and 

 under the trunk of the abdominal aorta, collecting the venous 

 blood chiefly from the surrounding muscular parts, and it 

 terminates in the great sinus venosus behind the auricle of 



