Subperiosteal hemorrhage is a sign distinctive of infantile scurvy, although it must be borne in mind that it may take place in the scurvy of adults. It involves most frequently the lower end of the femur and the tibia, but occurs in connection with the humerus, the mandible, the scapula and other bones.[47] The hemorrhage usually manifests itself as a swelling which appears suddenly at the lower end of the femur or femora. It is brought about by trauma, at times in the course of diapering, or by manipulation in testing for local tenderness. The swelling is very tender, and varies in size from an enlargement which is difficult to appreciate, to one which renders the leg fully twice its normal circumference (Fig. 18). It may involve merely a small part of the long bone or extend up or down the shaft for a long distance. As might be supposed from the nature of this lesion, the enlargement persists for weeks, frequently long after the gums and the general symptoms have disappeared. During this period it becomes harder and less tender, and may develop the consistency of bone; it is in this stage that such swellings have been diagnosed as new growths, and that incision or even amputation of the leg has been resorted to. In subacute cases the swelling--which must be regarded as hemorrhagic rather than scorbutic--may be absorbed gradually in spite of the fact that no antiscorbutic food has been given. This has led to the mistaken conclusion that the scurvy has been cured without dietetic treatment. [47] There seems to be some misconception as to the pathogenesis of the subperiosteal hemorrhage in scurvy. In most reports this lesion is described as if it resulted from a hemorrhage burrowing its way beneath the periosteum and raising it from the subjacent bone. In point of fact, such an event is impossible, as will be fully realized when one experiences the great difficulty in separating periosteum from normal bone. The scorbutic process involves the periosteum so that it is no longer normal but becomes insecurely attached to the shaft of the bone, and is readily stripped off by hemorrhage. Subperiosteal hemorrhage may be clearly seen by means of the fluoroscope or in X-ray photographs (Figs. 16 and 17). The shaft of the bone appears surmounted by an elongated blood-clot, which is more or less distinct according to its age and density. It may become calcified, as clearly seen in figures. More often the periosteum undergoes calcification or ossification, especially near the site of the separation of the epiphysis. This gives rise to a bizarre radiographic picture which may be difficult to interpret--the opaque strip or streamer being almost unrecognizable as periosteum (Fig. 17). [Illustration: FIG. 16.--Infant 11 months old. Separation of lower epiphysis of femur. Fraying of end of femur and head of tibia. Subperiosteal hemorrhage surrounding lower part of shaft of femur, with calcification of periosteum and of clot.]