The present report describes two anomalous cases of the right subclavian artery as the last branch of the aortic arch, which were encountered in the female Japanese cadaver of 74 years old (case 1) and in the male one of 71 years old (case 2).
In both cases the following branches arise in turn from the aortic arch with normal course. They are 1. the bicarotid artery, 2. the left subclavian artery and 3. the right subclavian artery as the last branch. The short bicarotid artery is soon divided into the right and left common carotid arteries which takes a normal course respectively. The left subclavian artery courses normally with the left vertebral artery leaving at its superior wall. The right subclavian artery arises from the postero-superior wall of the aortic arch with the so-called “diverticulum” at its origin. The artery runs backwards shortly at first. Then it bends sharply to the right and runs transversally behind the esophagus, thereby causing depression of the esophagus on its posterior wall. The right vertebral artery arises from the right subclavian artery.
These two anomalous cases belongs to type G of Adachi's classification (1928) of the aortic arch variations, and also to type H of Williams-Nakagawa's classification (1932) for having the bicarotid artery. Suzuki (1894) has reported the first case of type G in Japan, and these two are the 67th and 68th cases as far as we know.