The abdominal aorta ends by dividing into two trunks, named the common iliac arteries. The bifurcation usually takes place on the body of the fourth lumbar vertebra, a little to the left of the middle line. The point here indicated will be found nearly on a level with a line drawn from one crista of the ilium to the other, and is opposite to the left side of the umbilicus. It should, however, be observed, that the place of division is very inconstant in its position, as will be seen from the following statement.
In more than three-fourths of a considerable number of cases the aorta divided either upon the fourth lumbar vertebra, or upon the intervertebral disc below it ;in one case in nine it was below, and in about one in eleven above the space thus indicated.— In ten bodies out of every thirteen, the division of the -real artery took place within half an inch above or below the level of the crest ot the ilium ; and it occurred more frequently below than above that space.
The highest point at which the bifurcation of the aorta has been seen to take place is immediately after the origin of the right renal artery. In this case (only one is recorded) the two parts resulting from the division or the vessel were connected by a transverse branch, and then divided each into the external and internal iliac arteries.