THE PRESERVATION OF MATERIAL. 285 
At the time of beginning the embalming process the operator 
should have before him the reservoir, suspended at a height of 
about three feet, and a column of fluid, free from air-bubbles or 
foreign material to the tip of the cannula. This condition must 
be maintained throughout the operation. If at any time the 
pressure falls in the apparatus sufficiently to admit air, or allow 
coagulated blood to run back through the cannula, there is almost 
certain to be trouble, not only with the specimen under treatment, 
but also others which come after. The column of fluid is held back 
until the proper time by a clamp placed on the rubber tubing. 
The animal is killed by administering ether or illuminating gas. 
It is placed on its back on the table, with the head away from the 
operator. The skin is first divided by a small incision on the inner 
side of the right thigh.* By inserting the fingers well down into 
the incision, the skin may be torn backward and toward the ventral 
middle line, and at the same time the superficial epigastric vessels 
will be carried with the subcutaneous tissue well out of the oper- 
ator’s way. Small portions of the inner surface of the thigh and 
of the abdominal wall will be exposed. The white cord repre- 
senting the inguinal ligament lies in the bottom of the inguinal 
furrow. Appearing from beneath the ligament in this position, 
and passing to the surface of the thigh are the femoral nerve, 
artery, and vein, covered by an exceedingly thin layer of muscle 
belonging to the sartorius. The three structures may be separated 
from one another, and the muscle pulled away at the same time, 
by working lengthwise along the structures with the fine forceps. 
The artery must be thoroughly cleared for about 3 cm. from the 
inguinal ligament. Care must be exercised in this operation to 
avoid breaking its branches or the tributaries of the vein. The 
artery lies in front of the vein and is distinguishable by its smaller 
size, flattened or collapsed condition, and by its white coloration. 
The vein will be found greatly distended with blood. The nerve 
lies in front and partly on the lateral side of the artery. 
When the femoral artery has been fully exposed, a ligature of 
coarse thread, previously moistened, may be passed around its base, 
*The embalming may be done from the common carotid artery of the neck, a 
vessel much larger than the femoral artery and therefore easier of manipulation. 
This is not recommended, however, because of the damage done to various 
important structures of the cervical region. 
