SOME ABNORMALITIES OF THE VERTEBRAL ARTERY 1 
By Miguel Canizares 
Of the Department of Anatomy, University of the Philippines, Manila 
ONE PLATE AND FIVE TEXT FIGURES 
The considerable number of marked abnormalities of the ver- 
tebral artery met with in the department of anatomy in the 
course of our dissections there within the last two years, and 
their apparent practical importance and embryological signifi- 
cance, suggested the preparation of this report on the subject. 
The observations were made on forty cadavers used in the 
dissecting rooms of the College of Medicine and Surgery, Uni- 
versity of the Philippines. The cases were numbered from 1 
to 40. 
It is well known that the vertebral artery is one of the largest 
and most constant branches of the first portion of the subclavian, 
and that it has a different origin on each side. On the right 
side the artery arises from the subclavian about 2 centimeters 
from the origin of the latter from the innominate. On the left 
side, it arises from the most prominent part of the arch of the 
subclavian, close to the medial edge of the scalenus anterior 
muscle. On both sides it first ascends to the foramen transversa- 
rium of the sixth cervical vertebra and, having passed that fora- 
men and the foramina of the succeeding cervical vertebrae as high 
as the epistropheus, it turns laterally and ascends to the foramen 
of the transverse process of the atlas. From that point it turns 
backward behind the articular process and, after piercing the 
posterior occipito-atlantoid membrane and the dura mater, enters 
the cranium through the foramen magnum. Both vertebral ar- 
teries terminate at the lower portion of the pons varolii by 
anastomosing to form the basilar artery. 
While numerous observations on variations in the entrance 
of the vertebral artery to the foramen transversarium have been 
recorded, only a few reports on the abnormalities of its origin 
have been found by me. 
Bean, (2) in one hundred twenty-nine cases studied, found only 
1 Read before the IV Asamblea Regional de Medicos y Farmaceuticos 
de Filipinas, February 5, 1918. 
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