A MANUAL OF ZOOLOGY 65 



Make a diagram representing the venous system as far as 

 studied. 



What is meant hy a portal system? It will he noted 

 that the frog has two portal systems: the renal and the 

 hepatic. Trace hack the anterior abdominal vein to the 

 posterior part of the body and find that it receives blood 

 from the femoral veins. It will be found that the femoral 

 vein branches, one branch going to the kidney; this is the 

 renal portal vein. The hepatic portal system is formed 

 partly by the anterior abdominal vein, and partly by veins 

 returning blood from the alim-entary canal. Look for the 

 hepatic portal vein. Near the point where the branches 

 of the anterior abdominal veins go off to the liver, look 

 for the gastric vein, the intestinal veins, and the splenic 

 vein. Make a diagram of the portal system. 



Arteries — Distend the oesophagus with a roll of paper 

 or with a pencil. Clear off the arteries as in the case of 

 the veins. Note the division of the truncus arteriosus into 

 two branches, each of which subdivides into three arches: 

 the carotid arch, the systemic arch, and the pulmo-cuta- 

 neous arch. The most anterior of the three arches is the 

 carotid arch. It gives off a branch to the tongue, the 

 lingual artery. Find the carotid gland on this branch. 

 Trace the carotid artery around the oesophagus to its 

 dorsal surface and thence to the skull where It divides 

 into twaiPbranches, the external and the internal carotid 

 arteries. The middle of the three arches is the systemic 

 arch. Trace this around the oesophagus and note that it 

 joins with .its fellow from the opposite side In the region 

 of the kidneys to form the dorsal aorta. Note four 

 branches given off before this union: the lingual artery, 

 which supplies blood to the larynx, the oesophageal, the 

 occipito-vertebral, and the subclavian artery. Follow it 

 back of the union to the dorsal aorta and find four 

 branches: the coeliaco-mesenteric. It supplies with blood 

 the urogenital arteries, the" lumbar arteries, hemorrhoidal 

 artery. Note the division of the aorta into the great ar- 

 teries, the iliac arteries. These supply blood to what? 

 The most posterior of the three arches is the pulmo-cuta- 

 neous arch. It divides at about the level of the carotid 



