32 C. W. M. Poynter 
of development. As already pointed out, objections to this ar- 
rangement are appreciated and more data or a different viewpoint 
might suggest an entirely different classification. 
1. Right fourth arch obliterated, right dorsal root persists and 
is represented in the right subclavian, which is the last branch 
from the arch. 
2. Right fourth arch persists and is represented in the proxi- 
mal portion of the right vertebral, right dorsal root persists and 
is represented in the beginning of the right subclavian. 
3. Right fourth arch persists and is represented normally, the 
right dorsal root is present and is represented in the proximal 
portion of the right vertebral. 
4. Obliteration of the fourth left arch and dorsal connection 
with the fifth arch, persistence of the left pulmonary arch. 
5. Obliteration of the dorsal connection between the fourth 
and pulmonic arches, persistence of the left pulmonary arch. 
6. Obliteration of the right third arch, persistence of the dorsal 
connection between the third and fourth arches. 
7. Obliteration of the third left arch, persistence of the dorsal 
connection between the left third and fourth arches. 
8. Obliteration of the third arch and dorsal roots beyond. 
1. Right fourth arch is obliterated, right dorsal root persists 
and is represented in the right subclavian artery, which is the last 
branch of the arch. 
(a) Cases in which the right subclavian passes between the 
cesophagus and vertebral column. 
(b) Cases in which the right subclavian passes between the 
trachea and cesophagus. 
(c) Cases in which the right subclavian has a pretracheal 
course. . 
(d) Cases in which this anomaly is seen in conjunction with 
irregularities in arrangement or number of branches springing 
from the arch. 
(a) The origin of the right subclavian artery from the de- 
scending aorta is not a rare irregularity but perhaps on account 
of its unusual appearance it has received more attention than any 
other anomaly considered in this paper. The major portion of 
260 
SS eee 
