THE FROG 25 
and supply the kidneys, fat-bodies, sexual organs and the ducts 
of the urogenital system. Those arteries that are distributed to 
the kidneys alone are sometimes called renal arteries. 
The lumbar arteries are small vessels, variable in number and 
position, passing to the neighboring dorsal body wall and to the 
spinal cord. 
The posterior or inferior mesenteric supplies the dorsal side 
of the rectum, and in the female sends branches to the uteri.. 
The large iliac arteries are produced by the bifurcation of the 
dorsal aorta. A short distance behind the bifurcation each 
artery gives off a branch which divides into an epigastric artery 
supplying the ventral body wall, and a recto-vesical to the rectum 
and bladder. Further on the iliac artery gives off the femoral 
artery to the lateral muscles of the body wall and the hip joints ; 
it then continues down the thigh as the sciatic artery. The iliac 
artery and its branches can be studied from the body cavity. To 
expose the sciatic artery proceed as follows: Mark the point 
where the artery leaves the body cavity by thrusting a pin through 
the body wall to the dorsal surface. Remove the skin from the 
dorsal surface of the body and leg; dissect away the muscle and 
connective tissue posterior to the point indicated by the pin and 
expose the sciatic artery. Follow the sciatic artery down the 
dorsal side of the leg by forcing apart the great muscles in this 
region. 
3. The pulmo-cutaneous arch is the most posterior of the aortic 
arches. A short distance from its origin it divides into two 
branches, as follows: 
The pulmonary artery passes straight to the lung. At the 
root of the lung it divides into a number of branches which run 
toward the tip of the lung, each giving off branches to the interior 
trabecule. 
The cutaneous artery at first turns laterally, slightly forward 
and dorsalward, crossing the systemic arch; it then turns sharply 
dorsalward. To trace its further course turn the frog on its 
ventral surface, turn back the flaps of skin on the dorsal surface, 
ard carefully dissect away the muscle just posterior to the tym- 
panum. The cutaneous artery will then be seen emerging from 
the body cavity just in front of the suprascapula. Here it divides 
