452 Philippine Journal of Science ww 



three instances of the abnormality in the origin of the left ver- 

 tebral artery. In these the vessel arose directly from the arch 

 of the aorta between the left common carotid and the left sub- 

 clavian. He also found, in the same series, five cases of varia- 

 tion. In every case it arose from a common trunk, from part 1 

 of the subclavian in association with other arteries ; three times 

 with the inferior thyroid; once with the thyroid axis; and in 

 one instance the right vertebral artery was double. 



While it is a well-known fact that normally only three branches 

 are given off from the aortic arch, yet there are cases where 

 four or more vessels take origin from it. In the great majority 

 of such instances, according to Thane, (8) the left vertebral ar- 

 tery originates from the arch between the left common carotid 

 and the left subclavian, and only in rare instances between the 

 right common carotid and the right subclavian. 



In my series, I found two cases where the left vertebral artery 

 originated from the aortic arch between the left common carotid 

 and the left subclavian. In one instance (case 38) it ascended 

 in front of the transverse processes of the lower cervical verte- 

 brae until it reached the level of the third vertebra, there en- 

 tering the foramen transversarium. In case 39, after following 

 a similar vertical course, it entered the transverse foramen of 

 the fifth cervical vertebra. The right vertebral artery in both 

 cases was entirely normal (see Plate I, figs. 1 and 2). 



Bean's observations, as well as mine, appear to confirm 

 Thane's statement as to the more frequent aortic origin of the 

 left vertebral artery between the left common carotid and the 

 left subclavian. 



Thirteen of the remaining cases in my series, while apparently 

 normal in origin, showed abnormalities in the point of entrance 

 to the foramen transversarium. To this number must be added 

 the two cases described above which, besides having abnormal 

 origin, also showed variations in the point of entrance to the 

 transverse foramina. 



The cases are classified into two groups ; namely, cases show- 

 ing the same bilateral point of entrance and cases in which the 

 point of entrance differed on both sides. 



There were six cases in group 1 (see Table I). In four the 

 arteries entered the transverse foramen of the seventh cervical 

 vertebra ; in one, the foramen of the fifth ; and in the other, that 

 of the fourth cervical vertebra. 



Nine cases were placed under group 2 (see Table II). Here 

 there were five instances where the right artery entered the 



