ove and below, thereby conforming
exactly with the upper and lower limbs, which manifest unmistakable
points of analogy.

The branches which spring from the aortic arch above are destined to
supply the head and upper limbs. They are, H, the innominate artery, and
I K, the left common carotid and subclavian arteries. The branches which
spring from the other extremity of the aorta are disposed for the
support of the pelvis and lower limbs; they are the right and left
common iliac arteries, L M. These vessels exhibit, at both ends of the
main aortic trunk, a remarkable analogy; and as the knowledge of this
fact may serve to lighten the dry and weary detail of descriptive
anatomy, at the same time that it points directly to views of practical
import, I may be allowed briefly to remark upon it as follows:--

The vessels which spring from both ends of the aorta, as seen in Plate
25, are represented in what is called their normal character--that is,
while three vessels, H I K, spring separately from the aortic arch
above, only two vessels, L and M, arise from the aorta below. Let the
anatomist now recall to mind the "peculiarities" which at times appear
amongst the vessels, H I K, above, and he will find that some of them
absolutely correspond to the normal arrangement of the vessels, L M,
below. And if he will consider the "peculiarities" which occur to the
normal order of the vessels, L M, below, he will find that some of these
correspond exactly to the normal order of the vessels above. Thus, when
I K of the left side join into a common trunk, this resembles the
innominate artery, H, of the right side, and then both these vessels
perfectly correspond with the two common iliac arteries below. When, on
the other hand, L and M, the common iliac arteries, divide,
immediately after leaving the aortic trunk, into two pairs of branches,
they correspond to the abnormal condition of the vessels, H I K, above;
where H, immediately after leaving the aortic arch, divides into two
branches, like I K. With this generalization upon the normal and
abnormal facts of arrangement, exhibited among the vessels arising from
both ends of the aorta, I furnish to the reader the idea that the
vessels, H I K, above may present of the same figure as the vessels, L
M, below, and these latter may assume the character of H I K, above.
Whenever, therefore, either set of vessels becomes the subject of
operation, such as having a ligature applied to them,