114 . C. W. M. Poynter 
Fic. 8. This figure is adapted from Hochstetter’s (1906) fig. 118, show- 
ing the development of the vertebral arteries; it differs in no essential 
detail from fig. 6, above, which was suggested by one of his earlier figures. 
Fic. 9. A schematic representation of the development in cases of right 
aortic arch, in which there is present a left innominate; see Sect. II, C, 1. 
Fic. 10. A schematic representation of the development in cases of right 
aortic arch in which the left subclavian artery is the last branch of the 
arch; see Sect. II, C, 2. 
Fic. 11. This condition is similar to fig. 10, except that the left verte- 
bral artery springs apparently from the left common carotid instead of 
the left subclavian; see Sect. II, C, 3. This figure was first used by 
Brenner (1883) as fig. 5, Plate 17. 
Fic. 12. A schematic representation of the development in cases in 
which the right subclavian artery is the last branch from the arch. The 
figure was first used by Wood (1859) and has been variously modified to 
illustrate pre-tracheal and pre-cesophageal cases; for discussion see Sect. 
II, D, 1, and for illustration figs. 7, 25, 39 and 41. 
Fic. 13. This is similar to fig. 12 except that the right vertebral arises 
from the right common carotid instead of the right subclavian artery; see 
Sect: IT, D, 2) 
Fic. 14. A schematic representation of the development in cases in 
which the right vertebral artery arises from the aortic arch as the last 
branch; see Sect. II, D, 3. 
Fic. 15. A schematic representation of the development in cases in 
which the pulmonary artery through the ductus arteriosus gives origin to 
the dorsal aorta and the left subclavian artery; see Sect. II, D, 4. 
Fic. 16. Like fig. 15 except that the left subclavian artery seems to 
arise from the ascending aorta by a common trunk with the left common 
carotid artery; see Sect. II, D, 5. 
Fic. 17. A schematic representation of the development in cases in 
which the common carotid is absent and the internal and external carotids 
arise directly from the aortic arch; see Sect. II, D, 6 and 7. 
Fic. 18. A diagram showing varying degrees of torsion of the great 
vessels with corresponding arrangement of the bulbar and ventricular 
septa: A, torsion of 90 degrees; B, normal or torsion of 135 degrees; C, 
torsion greater than normal. In both 4 and C we must’ consider the con- 
dition normal except for the actual position of the vessels and the adapta- 
tion imposed on the ventricular loop. 
All of the figures on this plate are adapted from the figures of Roki- 
tansky (1875) and Robertson (1913a@) ; see Sect. I, C. 
Fic. 19. Diagrams representing a mirror picture of fig. 18 and illus- 
trating the possible positions of the vessels and septa in cases of situs 
viscerum transversus. 
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