Eobert Bennett Bean 



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Part I; the suprascapular artery rises from the internal mammary 

 artery. The type is of interest from this fact and because of its fre- 

 quent occurrence in the cases studied. 



Section B. — Desckiption of the Individual Branches. 



In its origin the vertebral artery is the most constant of all the 

 branches of the subclavian artery. It arises in every case, with three 

 exceptions, from the posterior and superior aspect of Part I, and is the 

 first and largest branch. It is associated with other arteries in its origin 



Fig. 6. Type V, occurring in 10% of the specimens. For index to lettering see 

 Fig. 1. 



from a common trunk but four times, with the inferior thyroid three 

 times, and the thyroid axis once. It comes from the arch of the aorta 

 between the origin of the left common carotid and the left subclavian 

 arteries three times. In one case on the right side the vertebral artery 

 is double, two small arteries arising from Part I and entering the 6th 

 vertebral foramen together. The artery enters the 4th foramen once; 

 the 5th, 4 times; the 6th, 88 times; and the 7th, 4 times. Tiedemann 

 states that this artery enters any one of the vertebral foramina from the 



