The existence of an osteogenetic substance capable of eliciting bone formation in undifferentiated connective tissue has been postulated by many investigators and has been sought for over 100 years.
When a nonosseous tissue is induced to change its cellular structure to bone, the process is called "bone induction." It is the result of contact of the inductor substance or cell with the nonosseous tissue.
Ossification has been found in soft tissues after the introduction of necrotic tissue (Bridges and Pritchard, 1958) or irritants (Hartely and Tanz, 1951). Bone has also been found after the injection of tissue extracts (Levander, 1938; Annersten, 1940; Bertelsen, 1944; LaCroix, 1945, 1951; Levander and Willstaedt, 1946), but results were not consistent, and Heinen (1949) proved that alcohol, which was the solvent used to extract the tissues, alone induced ossification.
Bone induction by transplanted urinary bladder mucosa presents an ideal field for investigation because of consistent