A case of dysembryogenesis of the aortic arches.

A medico-legal necropsy conducted on a stillborn child revealed certain abnormalities of the heart and the large vessels. Both the pulmonary artery and the aorta issued from the right ventricle, while the left ventricle communicated with the right superiorly and below the crest. There was no ductus arteriosus. As far the vessels were concerned, it was found that the aortic arch was directed rightwards, the innominate artery was absent and the right subclavian and common carotid issued directly from the arch. On the left, too, it was noted that the subclavian issued from the left branch of the pulmonary artery. If is suggested that these alterations were the result of primary obliteration of the left 4th aortic arch. This would explain both the dextroversion of the final arch and the absence of the anonymous artery. A further outcome would be prevention of the normal formation of the left subclavian, and its derivation from the left component of the 6th pair of aortic arches. Histological sections of the large vessels examined were prepared for investigation under the light microscope.