XIII.] THE FROG. 235 



b. Turn the animal over and follow one of these 

 trunks back : it will be found to be continuous 

 with the sciatic vein, which ends in the pelvis 

 by dividing into this and another (renal portai) 

 vessel. 



c. Trace the anterior abdominal vein forwards : it 

 divides into two branches, one of which goes to 

 the right and the other to the left lobe of the 

 liver. 



2. Raise the liver, and note the vena portse which enters 

 its lower surface; it is formed by the union of a vein 

 (gastric) from the stomach with one (lieno-intestinal) 

 from the spleen and intestines. The gastric division 

 of the vena portae communicates by a large branch 

 with the left division of the anterior abdominal vein. 



3- The veins of the head and neck and fore-limbs. 



a. Remove the liver, being careful not to injure 

 the inferior vena cava beneath it. 



b. Pass a bit of glass tube down the frog's gullet 

 (in order to stretch out the neighbouring parts) 

 and clean the aortic arches : passing in front 

 of each aortic arch, near its point of division is 



c. The external jugular vein, running up the side of 

 the throat towards the angle of the lower jaw 

 and receiving the veins of the mandibular and 

 lingual regions. 



d. Follow this vein down towards the heart : a 

 little way below the aortic arch it is joined by 

 another large vein 



e. The subdavian: follow this outwards; it will 

 be found to be formed mainly by the union 



