Marcelle Megret has assembled a comprehensive collection of radiographie images during her work in the field of com­ puted tomography of the cranial skeleton. This collection and her experience have made it possible for her to prepare these exercises in radiological diagnosis concerned exclusively with craniofacial tomodensitometry. The viewer will appreciate the choice of original docu­ ments of the highest quality, and also note the delicacy of execution of the diagrams, all drawn by the author herself. Marcelle Megret, like most of my students, conceives and carries out the schematas herself. The requirements concern­ ing certainty, strictness, precision, and objectivity would lead her to agree with Ludwig Wittgenstein's observations that since certain things cannot be said they must be shown, and that rules are insufficient when there are no examples. I should like this book to be successful. It inaugurates Marcelle Megret's career as an author and is an honor to the University of Geneva.