It is sometimes impossible to procure patients with typical dental changes when most desired. It is also difficult at times to demonstrate these changes, except to very small groups, especially if the child is nervous or excitable. Plaster casts of the mouth and teeth and photographs and lantern slides of these casts eliminate much of the uncertainty in teaching these conditions. There are certain changes in the contour of the jaw—"square corners," etc., that have been pointed out as occurring more often in congenital syphilis. We are not at present concerned with these changes or the height and width of the palatine arch or other bony deformities that belong in the group with the square shaped head, undershot jaw, depressed nasal bridge, etc., that are found in a fairly large percentage of these congenitally syphilitic children. The significant dental defects are found only in the permanent teeth. It is generally