THE VEINS. 25 
and indirectly from other viscera and from the hind 
limbs. It receives the following veins :— 
i. The right and left hepatic veins: from the liver: 
these open into the vena cava inferior just before 
it joins the sinus venosus. 
ii. The renal veins: from the kidneys: of these there 
are four or five on each side which open into, or 
rather form by their union, the inferior vena cava. 
The most anterior of these receive the veins 
from the fat bodies. 
ii, The ovarian veins (in the female), or spermatic 
veins (in the male); returning blood from the 
ovaries or testes. They are usually four or five 
in number on each side, and open into the vena 
cava inferior between the renal veins. 
II, Vein opening into the Left Auricle. 
a, The pulmonary vein: formed by the union of the 
right and left pulmonary veins, returning to the heart 
the blood from the right and left lungs respectively. 
Each pulmonary vein runs along the inner side of its 
lung. 
III. The Portal Systems. 
A portal vein is one which, returning blood from the capil- 
laries of some part, breaks up before reaching the heart into a 
second set of capillaries within some other organ ; these again 
unite to form a vein which carries the blood to the heart. In 
the frog there are two portal systems, one supplying the kidneys, 
and the other the liver. 
a. The renal portal system. 
Trace back the anterior abdominal vein to the hinder end of the 
body, where it will be seen to be formed by the union of the two 
pelvic veins. ollow back the pelvic vein of the right side to the 
base of the hind limb; here zt will be seen to be one of two 
branches into which the femoral vein (the large vein returning 
blood from the hind limb) divides. The other branch of the 
femoral vein is the renal portal vein, which is to be followed to 
the outer side of the kidney 
