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IOWA ACADEMY OF SCIENCE Voi,. XI^-^II, 1920 
artery. A number of cases are observed where the intercostal and 
mammary arteries formed a short innominate in common as is 
shown in figures 4 and 7. In one rabbit (Fig. 3, V) the vertebral ar- 
tery of this side branches from the cephalic surface of the arch of 
the aorta at about its junction with the subclavian artery and in this 
case it is comparatively a much larger vessel than normal. In 
this specimen also the transverse scapular and mammary arteries 
have their origin some distance cephalad, and the interval between 
the intercostal and mammary arteries is very noticeable. In no 
case is there found an innominate formed by the left subclavian 
and the left common carotid arteries, which of course is the 
typical avian condition, and which has been described as occurring 
in most apes, and somewhat more rarely has been noted in the 
human. In three cases, however, varying in degrees, as shown 
in figures 6, 8 and 10, the left common carotid artery is a separate 
branch from the arch of the aorta, and in these the condition 
closely simulates the normal condition found in the human. In 
one instance the points of origin of the vertebral and the trans- 
verse scapular arteries are interchanged as shown in figure 2, 
and in another, figure 5, the vertebral artery arises from the 
latero-caudal surface of the subclavian in the same manner but 
distal to the intercostal and mammary cervical vertebrae. In the 
last specimen also a number of excessory blood vessels are noted, 
some of which parallel the mammary, others the intercostal ar- 
teries. 
The subclavian artery of the right side. The blood vessels of 
this side which take their origin from the subclavian artery seem 
less variable in their relationships than those just described. There 
is the formation of what may be termed a corona in several in- 
stances, but this is with but one exception formed relatively close 
to the innominate, or to that portion close to the bifurcation of 
the innominate which forms the subclavian and right carotid 
arteries. Such a condition is typically shown in figure 5, where 
the vessels spread out in fan-shape formation about the sub- 
clavian. In one instance, the vertebral artery (Fig. 2, V) origi- 
nates well cephalad and on the lateral surface of the right common 
carotid artery, so that its displacement from its usual position 
is rather striking. As. regards the interrelation of the intercostal 
and internal mammary arteries all sorts of gradations of inter- 
vals exist from the formation of a conspicuous elongated innomi- 
nate as is indicated in figure 3, or a much reduced innominate 
as shown in figure 11, to the more or less widely separated 
