as evidence in such cases. You know that it is impossible for any one to take an accurate impression of the teeth and alveolus with any of the wax or plastic materials, and models made from such impressions ought no longer to be accepted as evidence, for at best

they serve only as a base of conjecture. Models should be made. with the same degree of skill that would be exercised in making the finest fillings, bridges, or dentures. When placed in articulation we should be able to examine them from every point, that we may study carefully the relation of each occlusal plane, the position and direction of each root, as shown by the next picture (Fig. 18). Such models are of lasting scientific value, and a collection. of them forms the most valuable library of orthodontic literature. I should like to show you many more models belonging to this

great class, and the accurate measurements from which have been determined how much the very apices of the roots have been shifted by