Inject the femoral artery of the specimen with either five per cent. formalin, or with the mixture of five per cent. formalin and glycerine, exactly as for the muscles. Then, without removing the canula or waiting, inject the artery with red starch. This is prepared as follows:
Mix together equal volumes of vermilion (or red lead), glycerine, and five per cent. formalin. Grind these together in a mortar, so as to destroy the lumps; strain the resulting mixture through fine muslin. This color mixture can be preserved in a closed bottle till it is to be used. Then mix together one volume of dry starch, one and one-fourth volumes of five per cent. formalin, and one-fourth volume of the color mixture. See that no lumps are present.
Inject the above red starch mass into the femoral artery. It will drive into the veins the formalin already injected, and the arteries will be filled with the red starch.
The veins need not be injected, as they will be found to be filled with the formalin mixture, colored by the blood, so that they can be traced without great difficulty.
Dissection of Blood-vessels.—In general the arteries and veins will be traced together. It is an excellent plan to make a sketch of each vessel as it is dissected, showing its origin, branches, and name. This will be a great aid to the memory and will be of much assistance in reviewing the vessels. The sketches can later be combined into a well-ordered drawing. The description of each vessel must of course be studied as the vessel is dissected.
In tracing blood-vessels do not grasp them between the forceps-blades, but handle them by taking hold with the forceps of the connective-tissue coats of the vessels. Do not use the scalpel, but pull away the connective tissue and fat with fine forceps, using two pairs of forceps or one forceps and the tracer.
Variations are especially common in the blood-vessels, and the student must not be surprised to find considerable deviations from the conditions described and figured in the text. These variations usually present nothing new in principle and are easily understood by comparing them with the structures described.
Directions for Dissecting the Blood-vessels.—Make a median longitudinal incision through the skin from the symphysis of the jaw to the caudal end of the xiphoid process. About three or four centimeters caudad of the cranial end of the sternum make an incision at nearly right angles to this, passing from the first incision on the ventral side of the left arm about to the elbow. Reflect the flaps of skin, so as to uncover the left side of the thorax and the under surface of the arm, exposing the pectoral muscles. Isolate and transect the pectoral muscles one at a time, cutting each near its thoracic attachment. (The muscles ([p. 145]) should be reviewed at the same time.) In this way the nerves and blood-vessels of the axilla are exposed ([Fig. 122], [p. 295]).
Find the axillary artery and vein ([Fig. 122], f and g) emerging from the thorax just craniad of the first rib, along with the nerves of the brachial plexus. Remove connective tissue, etc., so that the vessels and nerves are well isolated as they pass out of the thorax. Take great pains not to puncture the vessels, particularly the veins.
Then remove the left side of the thorax by cutting through the first rib near its sternal end and then near its dorsal end, without injury to the vessels and nerves, cut the other ribs in the same way, and take out the thoracic wall.