A crude papain suspension when injected intraperitoneally into suckling rats for twenty-three to sixty-nine days produced malformation of the sternum, rib cage, vertebral column, and caudad ribs. Permanent cartilaginous disorganization and epiphyseal-plate closure resulted in shortened long bones and vertebral bodies. Rigidity of the vertebral column was produced by degeneration of the nucleus pulposus, characterized by precipitation of eosinophilic necrotic debris and final replacement by hyaline fibrocartilage.