28 THE FROG 
The anterior abdominal is formed by the union of the pelvic 
veins ; immediately beyond this point it receives the vesical veins 
from the bladder. It passes thence forward along the mid ventral 
body wall, receiving branches from the body wall, and opposite _ 
the liver it ascends to enter the substance of the liver. Just 
before reaching the liver it divides into three branches, two for 
the right and left lobes respectively and a third communicating 
with the hepatic portal vein. As the anterior abdominal vein 
turns up toward the liver it receives a small branch, the cardiac 
vein, from the base of the truncus arteriosus. 
The hepatic portal vein receives branches which bring blood 
from the stomach, intestine, spleen and pancreas. 
IF. After completing the above work on the circulatory system 
write in your notebook answers to the following questions: 
Through what arteries must blood pass from the heart to 
reach the lungs, the skin of the sides of the body, the liver, the 
small intestine, the kidneys, the hind limbs? 
Mention the veins (and other organs if any) through which the 
blood corpuscles must pass, before reaching the heart, from the 
following parts: the lungs, the skin of the sides of the body, the 
small intestine, the hind limbs (two routes). 
How does the blood entering the sinus venosus from the 
anterior venz cave compare with that entering from the posterior 
vena cava as regards: (1) oxygenation, (2) nutritive material, 
(3) waste products? State reasons for your answers. 
Before leaving the study of the blood-vascular system be sure 
you have gained clear ideas concerning the following points: 
The mode of action of the heart, the function of all the valves, 
the mode by which oxygenated blood and the non-oxygenated 
blood are kept separate (consult Holmes’ Biology of the Frog, 
pp. 277 to 279), the general course of the circulation, and the 
changes that occur in the blood in the different parts of the body. 
Observe the general conformity of the venous system to the 
arterial and account for the similarity. 
G. If possible observe in a living frog the beating of the 
posterior pair of lymph hearts (see Holmes’ Biology of the Frog, 
p. 281). These are situated just beneath the skin in a slight de- 
pression between each hip-joint and the dorsal median line. The 
