Arterial Anomalies 39 
3. This group presents a persistence of the right dorsal aorta 
represented in the proximal portion of the right vertebral artery ; 
for diagram see fig. 14. The branches of the arch are normal, 
but the right vertebral, instead of springing from the subclavian 
in the usual manner, arises from the descending aorta just below 
the arch, passing outward and upward behind the subclavian to 
reach its normal position. In these cases the vertebral originates 
through a lower segment than the subclavian and in this respect 
is the reversal of group 2. If there were no other change than 
the persistence of the two segmental arteries and the right dorsal 
aorta the picture would be one of a double arch. The fact that 
the right arch includes a connection between the two segmental 
arteries instead of the right fourth root could not be appreciated 
from an examination of the case. 
It seems to me that to explain these cases we must assume that 
the axillary plexus, page 10, which Goppert has shown is always 
present, early makes a connection with one of the upper seg- 
mental arteries, say the sixth, very near its origin from the aorta. 
With this pathway established the more distal portion of the seg- 
mental (sixth) atrophies; then, when the connections are estab- 
lished between the segmental arteries to make up the vertebral, 
either a more cephalic segmental will furnish the origin of the ver- 
tebral or a more distal one (seventh) ; in the former condition the 
vertebral may arise from the subclavian near the common carotid 
and enter a higher transverse foramen, Waldeyer (1909), or from 
the common carotid as in one of Brenner’s (1883) cases where it 
entered the fourth transverse foramen; in the latter, representing 
this group, the persistence of the right dorsal aorta is in com- 
pensation for the absence of other vertebral connections. The 
vertebral enters the seventh.or sixth foramen. 
The following cases representing the condition have been re- 
ported: 
Hyrtl (1859) 2 cases, Struthers (1875), Paterson (1884), Azuta (1905), 
Szawlowski (1906). 
4. Obliteration of the fourth left arch and dorsal root, per- 
sistence of the left pulmonary arch. In these cases the innomi- 
267 
