Arterial Anomalies Bu 
Garnier & Villemin (1909), Macalester (1909), Weiss (1909), Dickson 
& Frazer (1914), Reid (1914), Warren Museum I case. 
3. This group of cases would be representatives of double aortic 
arches except for the absence of the left dorsal root; the order of 
branches is a left innominate stem dividing into left common 
carotid and left vertebral, right common carotid, right subclavian 
and left subclavian. The condition is recognized by Piersol in his 
anatomy and figured as fig. 688; he suggests that it is the reverse 
of fig. 685 (our II, D, 2) but he does not label the left vertebral in 
the figure. 
Brenner (1883) first explained this condition and showed the 
relation of the inferior laryngeal nerve to the left vertebral ar- 
tery ; he expressed the idea of a “ widening” of the vertebral but 
now we know from Hochstetter’s work (1890) that the vertebral 
and subclavian represent different segmental vessels. Brenner’s 
case is figured Taf. 17, fig. 5, our fig. 11, and contains the addi- 
tional variation of a right vertebral springing from the arch be- 
tween the right common carotid and right subclavian. 
4. Of this group we also have only one example, that of Fox 
(1824) which presents a normal arrangement of the vascular 
arches in a case of complete situs viscerum transversus. It may 
be viewed as a reversal of group I above, considering the body 
as a whole; on the other hand it is interesting in the suggestion 
that the factors which produce situs transversus may not always 
be operative in the development of the arches. 
For other variations in cases of right aortic arch belonging to 
origin of vessels springing from the arch see III, B, 2, g; C, and 
UT 1D), 2a Gls 
D. Abnormal Obliteration or Persistence of Segments of the 
Arches or Dorsal Roots 
A number of more or less limited irregularities of development 
are included in this section. They are grouped in this way not 
because they are morphologically similar, for they represent very 
divergent patterns, but because they represent circumscribed or 
local effects of the factors which have disturbed the normal course 
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