458 
Philippine Journal of Science 
1910 
sponding intersegmental artery with the proximal part of the 
dorsal aortic stem, while the intersegmental arteries below atro- 
phied and disappeared after the formation of the corresponding 
foramina. 
External carotid 
Ventral aorta 
Right subclavian 
artery 
Right pulmonary 
artery 
Trunk of pulmonary artery 
-- Internal carotid 
-—Common carotid 
-- Aortic arch 
Vertebral artery 
6th dorsal inter- 
segmental artery) 
Ductus arteriosus 
artery 
Left pulmona'ry artery 
Dorsal aorta 
Fig. 5. Diagram, showing possible abnormal origin of left vertebral artery. 
SUMMARY 
Two of the forty cases showed abnormalities in origin of 
the vertebral artery; and fifteen, in point of entrance to the 
foramen transversarium. 
My findings confirm those of Bean and Thane with regard 
to the greater frequency of abnormalities of origin of the ver- 
tebral artery in the left side. 
Cases of unilateral variations in the point of entrance were 
almost twice as numerous as the bilateral ones. 
My percentages of both abnormalities were higher than those 
found by Bean. 
I am inclined to agree with Bean (p. 313) in ascribing this 
relatively high percentage of abnormalities of the vertebral ar- 
tery to the fact that “hybrids tend toward variation.” Filipinos 
undoubtedly must be considered a mixed race. 
I wish to acknowledge my indebtedness to Prof. Edward S. 
Ruth for the helpful suggestions and kindly interest he has 
given me in this work. 
