ALZHEIMER'S IS A DISEASE of classically "insidious onset." Since even healthy people become more forgetful as theyage, there's no way to pinpoint the first memory to fall victim to it. The problem was especially vexed in the case of my father, who not only was depressive and reserved and slightydeaf but also was talking strong medicines for other ailments. For a long time it was possible to chalk up his non sequiturs to his hearing impairment, his forgetfulness to his depression, his hallucinations to his medicines; and chalk them up we did.