452 ZOOLOGY SECT. 



side of the chest behind the root of the fore-limb. The right carotid 

 divides opposite the angle of the jaw into internal and external 

 carotids. The left carotid and left subclavian correspond in their 

 distribution and branching to the right carotid and right subclavian 

 respectively. The aorta, in passing through the thorax, gives off 

 a series of small paired intercostal arteries (i. cs.). In the abdomen 

 its first large branch is the cceliac artery (co3.) t which supplies the 

 liver, stomach, and spleen. Behind this it gives origin to the 

 anterior mesenteric (a. m.), which supplies the intestine and the 

 pancreas. Opposite the kidneys it gives off the two renal arteries (r.) 

 for the supply of these organs, and a good deal further back the 

 spermatic (spm.) or ovarian arteries for the testes or ovaries as the 

 case may be. Just in front of the origin of the spermatic arteries 

 is given off a posterior mesenteric (p.m.), which supplies the hinder 

 part of the rectum. A series of small lumbar arteries supply the 

 side-walls of the abdominal cavity. Posteriorly the dorsal aorta 

 divides to form the two common iliac arteries (c. il. a.) which 

 supply the pelvic cavity and hind-limbs, a small median sacral 

 (caudal) artery (ms. c.) passing backwards in the middle line to 

 supply the caudal region. 



The system of caval veins which open into the right auricle consists 

 of the right and left precavals and of the single postcaval. The right 

 precaval is formed by the union of the right jugular (e.ju.) vein and 

 right subclavian (scl. v.). The azygos vein (az. v.), the right anterior 

 intercostal (i.cs.), and the right anterior epigastric or internal mammary 

 also open into it. The left precaval receives a series of veins similar 

 to those forming the right, except that there is no azygos on the 

 left side (cf. p. 298). 



The postcaval vein (pt. c.) is formed in the hinder part of the 

 abdominal cavity by the union of the internal iliacs (i. il. v.) bringing 

 the blood from the back of the thighs. Shortly after its origin it 

 receives the two external iliacs (e. il. v.) coming from the hind- 

 limb. In front of this a pair of ilio-lumbar (il.) veins join it ; 

 a little farther forward a pair of spermatic (spm.) or ovarian 

 veins ; and opposite the kidneys a pair of renal veins (r.). From 

 the liver the blood is carried to the postcaval by the hepatic veins. 

 A pair of small posterior phrenic veins (p. ph.) bring the blood from 

 the diaphragm and open into the postcaval as it passes through 

 the substance of the latter. 



The hepatic portal system consists, as in other Vertebrates, of a 

 system of veins conveying blood from the various parts of the 

 alimentary canal to the liver, the trunks of the system uniting to 

 form the single large portal vein (Fig. 1100, p. v.). The principal 

 veins of the portal system are the lieno-gastric, duodenal, anterior 

 mesenteric, and posterior mesenteric. There is no trace of a renal 

 portal system. The red blood corpuscles are circular, bi-concave, 

 non-nucleated discs. 



