s,
according to the regions which it traverses. But, as in examining any
one of those parts irrespective of the others, many facts of chief
surgical importance are thereby obscured and overlooked, I propose to
consider the vessel as a whole, continuous from the aorta to where it
enters the popliteal space. The general course and position of the main
artery may be described as follows:--The abdominal aorta, A, bifurcates
on the body of the fourth lumbar vertebra. The level of the aortic
bifurcation corresponds with the situation of the navel in front, and
the crista ilii laterally. The aorta is in this situation borne so far
forwards by the lumbar spine as to occupy an almost central position in
the cavity of the abdomen. If the abdomen were pierced by two lines, one
extending from a little to the left side of the navel, horizontally
backwards to the fourth lumbar vertebra, and the other from immediately
over the middle of one crista ilii, transversely to a corresponding
point in the opposite side, these lines would intersect at the aortic
bifurcation. The two arteries, G G,* into which the aorta divides
symmetrically at the median line, diverge from one another in their
descent towards the two groins. As both vessels correspond in form and
relative position, the description of one will serve for the other.

While the thigh is abducted and rotated outwards, if a line be drawn
from the navel to a point, D, of the inguinal fold, midway between B,
the anterior iliac spine, and C, the symphysis pubis, and continued
thence to the inner condyle of the femur, it would indicate the general
course of the artery, G I W. In this course, the vessel may be regarded
as a main trunk, giving off at intervals large branches for the supply
of the pelvic organs, the abdominal parietes, and the thigh. From the
point where the vessel leaves the aorta, A, down to the inguinal fold,
D, it lies within the abdomen, and here, therefore, all operations
affecting the vessel are attended with more difficulty and danger than
elsewhere, in its course.

The artery of the lower limb, arising at the bifurcation of the aorta on
the fourth lumbar vertebra, descends obliquely outwards to the
sacra-iliac junction, and here it gives off its first branch, G,
(internal iliac,) to the pelvic organs. The main vessel is named common
iliac, at the interval between its origin from the aorta and the point
where it gives off the internal iliac branch. This interval i