Supernumerary ribs are not at all uncommon in man, nearly every medical museum having some examples. Cervical ribs are not rare. Gordon describes a young man of seventeen in whom there was a pair of supernumerary ribs attached to the cervical vertebrae. Bernhardt mentions an instance in which cervical ribs caused motor and sensory disturbances. Dumerin of Lyons showed an infant of eight days which had an arrested development of the 2d, 3d, 4th, and 5th ribs. Cases of deficient ribs are occasionally met. Wistar in 1818 gives an account of a person in whom one side of the thorax was at rest while the other performed the movements of breathing in the usual manner. In some cases we see fissure of the sternum, caused either by deficient union or absence of one of its constituent parts. In the most exaggerated cases these fissures permit the exit of the heart, and as a general rule ectopies of the heart are thus caused. Pavy has given a most remarkable case of sternal fissure in a young man of twenty-five, a native of Hamburg. He exhibited himself in one medical clinic after another all over Europe, and was always viewed with the greatest interest. In the median line, corresponding to the absence of sternum, was a longitudinal groove bounded on either side by a continuous hard ridge which articulated with the costal cartilages. The skin passed naturally over the chest from one side to another, but was raised at one part of the groove by a pulsatile swelling which occupied the position of the right auricle. The clavicle and the two margins of the sternum had no connections whatever, and below the groove was a hard substance corresponding to the ensiform cartilage, which, however, was very elastic, and allowed the patient, under the influence of the pectoral muscles, when the upper extremity was fixed, to open the groove to nearly the extent of three inches, which was more than twice its natural width. By approximating his arms he made the ends of his clavicles overlap. When he coughed, the right lung suddenly protruded from the chest through the groove and ascended a considerable distance above the clavicle into the neck. Between the clavicles another pulsatile swelling was easily felt but hardly seen, which was doubtless the arch of the aorta, as by putting the fingers on it one could feel a double shock, synchronous with distention and recoil of a vessel or opening and closing of the semilunar valves.