458 



Philippine Journal of Science 



1919 



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 -.J 



Right subclavian 

 artery 



Right pulmonari 

 artery 



Trunk of pulmonary artery 



— Internal carotid 



•~ — -Common carotid 



Aortic arch 



Vertebral artery 

 {6th dorsal inter- 

 segmental artery) 



•Ductus arteriosus 



-Subclavian artery 

 ''Left pulmonary artery 



-Dorsal ao»'fu 



Fie. 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. 



