3. Right subclavian artery.

4. Right common carotid artery.

5. Left subclavian artery.

6. Left common carotid artery.

7. Left axillary artery.

8. Coracoid attachment of the smaller pectoral muscle.

9. Subscapular muscle.

10. Coracoid head of the biceps muscle.

11. Tendon of the latissimus dorsi muscle.

12. Superior mesenteric artery, with its accompanying vein.

13. Left kidney.

[Illustration: Chest and abdomen, showing bones, blood vessels, muscles
and other internal organs.]
Plate 24

COMMENTARY ON PLATE 25.

THE RELATION OF THE PRINCIPAL BLOODVESSELS OF THE THORAX AND
ABDOMEN TO THE OSSEOUS SKELETON, ETC.

The arterial system of vessels assumes, in all cases, somewhat of the
character of the forms upon which they are distributed, or of the organs
which they supply. This mode of distribution becomes the more apparent,
according as we rise from particulars to take a view of the whole. With
the same ease that any piece of the osseous fabric, taken separately,
may be known, so may any one artery, taken apart from the rest, be
distinguished as to the place which it occupied, and the organs which it
supplied in the economy. The vascular skeleton, whether taken as a whole
or in parts, exhibits characteristics as apparent as are those of the
osseous skeleton itself. The main bloodvessel, A B C, of the trunk of
the body, possesses character, sui generis, just as the vertebral column
itself manifests. The main arteries of the head or limbs are as readily
distinguishable, the one from the other, as are the osseous fabrics of
the head and limbs. The visceral arteries are likewise moulded upon the
forms which they supply. But evidently the arterial system of vessels
conforms most strictly with the general design of the osseous skeleton.

In Plate 25, viewed as a whole, we find that as the vertebral column
stands central to the osseous skeleton, so does the aorta, A B C, take
the centre of the arterial skeleton. As the ribs jut symmetrically from
either side of the vertebral column, so do the intercostal arteries
follow them from their own points of origin in the aorta. The one side
of the osseous system is not more like the other than is the system of
vessels on one side like that of the other. And in addition to this fact
of a similarity of sides in the vascular as in the osseous skeleton, I
also remark that both extremities of the aorta divide into branches
which are similar to one another ab