Yea and Grey's Anatomy is a show, not a reference
grey's anatomy is a show. GRAY'S anatomy is the most comprehensive encyclopedia on anatomy published, and that's where the show got its title from, dumbass. i was wrong about the 1 in 8 stat, though.
from gray's anatomy:
http://www.bartleby.com/107/124.htmlVariations.—A third head (10 per cent.) to the Biceps brachii is occasionally found, arising at the upper and medial part of the Brachialis, with the fibers of which it is continuous, and inserted into the lacertus fibrosus and medial side of the tendon of the muscle. In most cases this additional slip lies behind the brachial artery in its coarse down the arm. In some instances the third head consists of two slips, which pass down, one in front of and the other behind the artery, concealing the vessel in the lower half of the arm. More rarely a fourth head occurs arising from the outer side of the humerus, from the intertubercular groove, or from the greater tubercle.
here endeth the lesson.