456 APPENDIX. 
jy. Pass a probe into the aorta. Introduce scissors behind the 
septal flap of the bicuspid valve and slit the neue without injury to 
the bicuspid valve. 
II. Dissection oF THE BLOOD-VESSELS. 
Preparation and Injection. —A new specimen must be prepared for 
the dissection of the blood-vessels. The same specimen may be 
used, if necessary, for the dissection of the peripheral nervous 
system,—one side being used for the blood-vessels, the other for the 
nerves,—but it is much better to use separate specimens for the two 
systems. ; 
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 Jumps 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 assist- 
ance 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 of grasp them between the forceps- 
blades, but handle them by taking hold with the forceps of the con- 
nective-tissue coats of the vessels. Do mof 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 longi- 
