Two cases of bifid ribs observed in the fourth and the fifth rib

Two cases of bifid rib were found in two cadavers during routine dissections at Iwate Medical University School of Dentistry. They were found in the fourth rib in one cadaver, and in the fifth rib in the other cadaver. In one case both the branching and the reunion of the rib occurred in the osseous part, and in the other case they occurred in the cartilage part. The space between the two branches was filled with presumably normal intercostal muscles. The blood supply had been maintained by small branches from the internal thoracic artery to the upper branch and the intercostal muscles. However, the intercostal nerves did not branch toward the upper branch but only ran along the lower margin of the lower branch of the bifid rib in both cases.