To the Editor:— The word "preventative" does not appear in Webster's Collegiate Dictionary . Perhaps the lexicographer omitted it because of a personal whim or prejudice (some people can carry their prejudices to extremes). A case in point is that of Dr. Ravenell, a former Army Surgeon, who used to teach a course in Preventive Medicine at the University of Missouri. At the opening session of the course, Dr. Ravenell was wont to announce that the grade would depend entirely on how well the student did in the final examination. He would then make the pronouncement that no matter how well the student mastered the subject, his final grade would be an "F" if he had the misfortune to label the examination "Preventative Medicine." In the June 15, 1964, issue ofThe Journal(vol 188) preventative appears on page 1005, right hand column, "to use quinidine as a preventative," and on