(_a_) _A pulmonary artery, running along the outer side of the whole
length of the lung._
(_b_) _A cutaneous artery, which at first runs forwards and upwards,
and then turns backwards, supplying the skin of the back and the
sides of the head._]
Make a complete sketch of the arterial system.
[Illustration: FIG. 7.--Arterial System of Xenopus and Rana.]
Cut out the heart, leaving attached to it as much as possible of the
large vessels.
Note the sinus venosus, truncus arteriosus, auricles, and ventricle.
Open the auricles and observe the division between them and the
openings of the veins passing into them.
Make a section through the auricles and ventricle noting the thick
muscular walls of the ventricle and the valves between it and the
auricles.
=Respiratory System and Alimentary System= (_continued_).
1. Remove the mylo-hyoid muscles to expose the hyoid apparatus. Pass
a seeker through the glottis to one of the lungs and slit it open
with a pair of scissors. Examine the structure of the lung.
2. Remove the whole of the alimentary canal with the lungs, liver,
pancreas, and spleen, by cutting through the œsophagus and the large
intestine before it joins the cloaca, and detaching it from the roof
of the body cavity without injuring the kidneys and the reproductive
organs.
Draw the complete alimentary canal.
[Illustration: FIG. 8.--Alimentary Canal of Xenopus and Rana.]
Urinogenital System.
Note the kidneys, two elongated, flattened, dark-red bodies lying one
on each side of the vertebral column towards the posterior end of the
abdominal cavity. From the outer edge of each kidney a ureter arises
and runs backward, opening into the cloaca on the dorsal side,
opposite the opening of the urinary bladder.
[_In the Frog the adrenal bodies may be seen on the ventral sides of
the kidneys as small yellow patches._]