96 Elementary Manual of Zoology. 
which is much smaller, receives the blood from the pulmo- 
nary veins. 
Follow down the anterior abdominal vein to the base of the legs, and 
make out where it branches to each thigh. Then follow it upwards 
towards the heart and endeavour to make out where it divides into 
branches, which enter different lobes of the liver, The anterior abdo- 
minal vein is one of the two channels by which the blood from the legs 
can return to the heart. The other being vzd the renal portal system. 
Cut away the anterior abdominal vein, and bend the liver over for- 
wards with your forceps, noticing the greenish gall bladder. Notice 
also the vene porte, which collect the blood which comes from the 
stomach and intestine, and pour it into the liver. i 
Cut away the liver and notice the large vena cava inferior below it, 
by which the blood returns frqm the liver and lower part of the body to 
the sinus venosus. Endeavour to make out the external jugular vein 
which passes dcwn in front of each aortic arch. Follow this vein to- 
wards the heart and endeavour to make out where it is joined by the 
sub-claviau vein from the front limb and the innominate vein from the 
back of the head and shoulder. The three together form the superior vena 
eava, through which the blood returns to the sinus venosus, whence it 
passes into the right auricle. 
Now trace up the aortic branches as far as you can, and endeavour to 
make out how they divide on either side into three great trunks. The 
anterior of these (carotid) supplies the head and throat; the middle 
(systemic aortic arch) runs round the gullet to join the corresponding 
arch on the other side, on its way giving off the sub-clavian artery to the 
fore limb ; while the posterior (pulmo-cutancous artery) supplies the 
lung and gives off a branch near the shoulder to the skin, 
Push aside the intestine and trace the inferior vena cava downwards 
to where it originates in branches from the pair of dark-coloured kid- 
neys, which lie in the posterior part of the body cavity. Push aside the 
kidneys also and notice the large vein (renal portal) which passes into 
the kidney from the hind limb. ‘This is the second channel 
through which the blood from the hind limb is able to return to the 
heart. ; 
Now cut through the membrane by which the intestine is held 
together. Push it aside, clear away the vena cava inferior between the 
kidneys, and below you will find the straight dorsal aorta lying above 
the vertebra. This vessel supplies blood to all the lower part of the 
bedy. Trace it both forwards and backwards as far as youcan. Ante. 
riorily it is formed by the junction of the two systemic aortic arches, 
while posteriorily it divides into the two iliac arteries, which supply the 
hind limbs. Between these two points it gives off numerous branches 
to the digestive tract, reproductive organs, kidneys and spleen. 
