Current orthodontic literature reiterates the contention that the inherited growth pattern determines the form of the human jaws and that the jawbones therefore cannot be modified or influenced. According to this contention, effective influence of any treatment is restricted to the alveolar bone. (Brodie, Broadbent, Hellman, Thompson, Mershon, Jackson.) The acceptance of this concept limits improvement in orthodontic therapy to the perfecting of mechanical, tooth-moving devices. More important, if the concept is fallacious, it precludes (if accepted) any clarification of the origin of dental and facial malformations. Because of the inherent defeatism of this contention of immutability, any contradictory theory deserves attention. Generally accepted biologic laws do not support the validity of the theory of immutability of the jawbones (Roux, Darwin, Russel). Through decades orthodontic research has favored the idea that extraalveolar areas can be influenced by treatment (Angle, Case, Baker). Moreover, histologic proof has been published 11 of bone transformations induced in areas other than the alveolar process, such as the temporomandibular joint, ramus, angle and lower border of the mandible. There remains a contradiction between, on one side, general biology and these findings and, on the other side, the conception of immutability of the jawbones. The clarification of this issue is fundamental to the understanding of the origin of dentofacial malformations as well as to improvement in the methods of their correction. In this essay new, clinical proof is added to previously published microscopic evidence that bone changes can be induced in extra-alveolar areas. In a mature Macacus rhesus monkey a complete and lasting change in occlusal relations was created without applying any forces to the teeth or to the alveolar process. No mechanical device was used but, by paralyzing masticatory muscles and thus disturbing the balance between muscular forces and the given resistance of the skeleton, an Angle Class III malocclusion was created in a previously normal animal within seventy-two days. This malocclusion has persisted for one year and a half to date, long after recuperation of the affected muscles. In a similar animal an Angle Class II malocclusion, with the associated anomalies of excessive overjet and overbite, was created by raising the bite through flat caps in the molar and premolar regions. The development of this Class II may be correlated with the first experiment where a Class III was created through weakening of the masticatory muscles; for raising the bite means strengthening (increased tone) through elongation of those same masticatory muscles whose weakening induced the Class III anomaly in the first experiment. The results of the experiments are significant in reference to the following points The experiments corroborate previously published histologic evidence of induced extra-alveolar bone transformations. The experiments suggest one possible cause of dental malformations, namely, a disharmony among the muscular forces, or between muscular forces and the architecture of the bone. The experiments point toward a possible means of influencing the occlusion without employing appliances or similar conventional apparatus, by directly modifying muscular strength or bony resistance, possibly even by influencing systemic factors. The experiments elucidate the necessity, in attempting improvement of orthodontic therapy, not of concentrating upon mechanical devices but rather of seeking means of modifying the skeleton.