THE AORTA OF THE RABBIT 
303 
after giving off the coronary arteries close to its junction with 
the left ventricle passes cephalad a short distance and then des- 
cribes a curve or a half circle and passes down the back, a little 
to the left of the ventral vertebrae. From the cephalic curve 
(arch) a comparatively large innominate or brachio-cephalic artery 
extends upward and a little to the right and soon bifurcates 
forming the left common carotid artery which passes immediately 
across the trachea to the left side of the neck, and a common 
trunk which gives rise to the right subclavian and the right com- 
mon carotid arteries. A second branch from the curve of the 
aorta is the left subclavian artery which passes laterad and for- 
ward to branch in various ways. Usually on this side the superior 
intercostal (costo-cervical) (Fig. 1, I) is the first branch to be 
given off, and this passes caudo-mediad. Just distal and in close 
juncture with the superior intercostal artery is the internal mam- 
mary artery, while just opposite arises the vertebral artery. Dis- 
tally the subclavian artery soon divides into the transverse scapu- 
lar (T) and axillary (X) arteries. On the right side the superior 
intercostal and mammary arteries arise from a common trunk, as 
also do the vertebral and transverse scapular arteries just opposite 
them. The axillary artery passes to the region of the forearm. 
In some cases the superficial cervical artery branches from the 
subclavian, but usually it is a branch of the transverse artery 
of either ade. 
• Variations of the subclavian artery of the left side. A number 
of interesting variations are noted in the order and sequential 
relationships of the various vessels arising from the left sub- 
clavian. Frequently the arteries originating from the subclavian 
artery are in close proximity to each other so> that a veritable 
corona of the vessels is formed. In some cases as shown in figures 
6 and 11 this takes place at quite a distance from the arch of the 
aorta, and can be called the long corona type, while in others 
typified in figures 9 and 10 and perhaps less conspicuously in 
figure 8, the corona formation is closely approximated to the 
aortic arch. Where the corona is formed, the usual order/ of 
the vessels may be described as normal, i.e., beginning with the 
vertebral artery originating on the cephalo-mesal surface of the 
subclavian, the transverse scapular, axillary, mammary, and inter- 
costal arteries followed in the cycle clockwise. In one specimen 
an interesting departure is noted, in that the intercostal artery 
(Fig. 6,i I) takes its origin from the vertebral so that there is 
formed in this case a very short innominate with the vertebral 
