ILLUSTRATIONS 
PLATE I 
FIG. 1. Diagrammatic sketch, showing abnormalities of origin and point 
of entrance of left vertebral artery in case 38. 
2. Diagrammatic sketch, showing abnormalities of origin and point 
of entrance of left vertebral artery in case 39. 
TEXT FIGURES 
FIG. 1. Diagram, showing the aortic arches and their derivatives in human 
embryos with normal origin of vertebral arteries (modified after 
Prentiss). 
2. Diagram, showing stage of five aortic arches and origin of the 
vertebral arteries (modified after Cunningham). 
3. Diagram, showing one possible abnormal origin of left vertebral 
artery. 
4. Diagram, showing another possible abnormal origin of the left 
vertebral artery. 
5. Diagram, showing possible abnormal origin of left vertebral artery. 
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