Growths of bone tissue in muscles and in their tendinous insertions after trauma, in muscle tissue about joints after dislocations or in soft tissues about a simple fracture of a bone or after a minor injury commonly are given such designations as traumatic myositis ossificans, parosteal callus or some other appropriately descriptive term. Summaries of the data on such growths have been written by Fay,1 Painter,2 Lewis,3 Carey,4 Gruca,5 von Dittrich,6 Goto,7 Geschickter8 and others. All these reviews have emphasized trauma as the initiating factor. No age group is immune, but the incidence is greatest in young men. Fay stated that this indicates merely the frequency of trauma in a group leading an active life. The usual sites of these traumatic osseous growths are those exposed to injury in occupation, avocation or accident. According to Cahier,9 three fifths of the bone