1. Open the abdominal cavity; find the superior mesenteric vein (p.
326, and Fig. 132) in the duodenal mesentery near the border of the
pancreas. Inject this in both directions with white starch and then
dissect the portal vein and its tributaries without injuring any of the
structures in the abdomen (p. 326, and Fig. 132).
2. Follow the inferior vena cava (p. 325) from the heart to the
diaphragm and then follow it to its tributaries in the abdominal cavity.
3. Dissect the branches of the abdominal aorta (p. 301) and of the
inferior vena cava (Fig. 126). Make diagrams of the vessels dissected
and review as far as necessary the viscera concerned.
V. The external iliac and its branches (vessels of the hind limbs) (pp.
309 and 329, and Figs. 127, 128, and 163).
Follow the branches of the external iliac arteries and the corresponding
veins in the same manner as the vessels of the arm were traced, cutting
the muscles only so far as absolutely necessary. Make diagrams of the
vessels dissected.
Make a diagram (_a_) of the arterial system as a whole; (_b_) of the
venous system as a whole.
THE LYMPHATIC SYSTEM (p. 330).
It will hardly be found practicable to have each student make a
dissection of the lymphatic system, and such parts of it as are to be
studied may best be shown on a specimen prepared for demonstration
purposes.
The thoracic duct and the receptaculum chyli may be demonstrated by the
following well-known method: A lean cat is fed with milk about two hours
before killing it. An egg may be beaten up with the milk to advantage.
Kill the cat with chloroform, and inject the arteries with colored
starch through the femoral, in the usual way. The thoracic duct, the
receptaculum chyli, and the lymphatics leading to the receptaculum chyli
will be colored white by the milk, and can therefore be easily followed.
For this purpose the abdomen should be opened, and the left side of the
thorax removed, as in the dissection of the blood-vessels. The thoracic
duct will be found at the left side of the aorta and may then be traced
in both directions.
For a more complete study of the lymphatics they should be injected.
This is done as follows: Make a glass canula with a small point, and
leave the point sharp. Connect this to the syringe by means of a rubber
tube. Use a saturated solution of soluble Prussian blue as injecting
fluid. Employ a freshly killed animal.
For injecting the lymphatics of the limbs, make with some pointed
instrument, as the tracer, a small hole in one of the pads on the sole
of the foot. Introduce the point of the canula into this opening and
inject the fluid. This will pass into the spaces in the connective
tissue of the pad, which will swell up, and the colored fluid will pass
from the connective-tissue spaces into the lymphatics. Pressure must be
maintained with the syringe for a considerable time,--fifteen minutes to
a half-hour for a good injection of the main trunks of the lymphatics of
the limbs. The movement of the fluid should be facilitated by pressing
and manipulating the limb at the same time with the hand,--in such a way
as will tend to drive the fluid proximad.
The lymphatics of the head may be injected in a similar manner, the
canula being introduced into the upper and lower lip, or into the bare
surface at the end of the nose.
The internal lymphatic vessels may be injected by injecting the
lymphatic glands with which they are connected. This may conveniently be
done as follows: Draw out to a fine point the tip of an ordinary pipette
or medicine-dropper. The point should be fine, but should taper rapidly
in a conical fashion, so that when the point is inserted the part of the
glass tube behind it will close up the opening.
Fill the pipette with soluble Prussian blue; insert the point into the
gland, and inject the fluid slowly. The lymphatic vessels passing from
the glands will be filled. By injecting thus the large lymphatic gland
(“pancreas Aselli”) in the mesentery, the abdominal lymphatics, the
receptaculum chyli, and the thoracic duct may be injected.
By using thin gelatine colored with Prussian blue as an injecting fluid
permanent preparations may be obtained; of course the process of
injection is then less simple, and should be looked up in some manual of
methods.