Eight True Ribs in Man

Abstract

IN the number of NATURE which appeared on November 1, 1888, there is a notice to the effect that “at one of the meetings of the Anatomical Society, during the session of the Medical Congress in Washington, Dr. Lamb, of the United States Army Medical Museum, spoke briefly of a singular phenomenon he had observed in his examination of human breast-bones. It was the occurrence, in a number of specimens, of an eighth rib, the cartilage that is usually found below the seventh rib being fully developed into a rib.” This description is somewhat ambiguous, but I presume it refers to the occasional elongation of the eighth costal cartilage in man, and its direct articulation with the sternum. At the time when I read this notice I was organizing a system of “collective investigation” in my class of practical anatomy, in Trinity College, Dublin, and I asked Mr. O. L. Robinson, one of my assistant demonstrators, to undertake the investigation of this point. During the last two months he has examined thirty subjects, and he has found the eighth costal cartilage united to the sternum in no less than five of these. In four subjects (two males and two females) the eighth cartilage of the right side alone showed this condition; in the remaining case (a male) the eighth cartilage on each side reached the breast-bone and articulated with its fellow in front of the upper part of the ziphi-sternum. The anomaly is therefore one of some frequency, seeing that it has been noted by Mr. Robinson in about 17 per cent, of the subjects which he has examined. I may mention that all the specimens are now in my possession.