Over the past 30 years, Dr. Seuss has endeared himself to millions of youngsters (and harried older types) with his tales of such giggle-producing creatures as "The Cat in the Hat" and "Yertle the Turtle." Now, finally, he's written a book for those he calls "obsolete children." It's the nicest thing to happen to "senior citizens" since Medicare. This time around, the Doctor enlists his jaunty rhymes and sprightly illustrations to present a not altogether tongue-in-cheek look at that unnerving ritual of aging, "the medical check-up." His reactions to the whole demeaning (and distinctly expensive) process are so wryly knowing he might well have entitled his opus "The Cynic in the Clinic." The medical profession, under Seuss' steady gaze, comes in for some hilarious--and pointed--joshing. The action takes place at the "Golden Years Clinic on Century Square for Spleen Readjustment and Muffler Repair." Here, after first undergoing an "Eyesight and Solvency Test" (the chart reads "Have you any idea how much money these tests are costing you?"), the grey-mustachioed hero meets a battery of specialists including "Von Crandall, the World-Renowned Ear Man" and "Dr. Pollen, the Allergy Whiz." These worthies pinch, prod and poke about in search of such maladies as "Prone Picker's Plight" and "Chimney Sweep's Stupor." Diets are devised--"What you like. . .forget it!" Seuss has a great deal of fun with the "Pill Drill," in which the hero must memorize the dosages of a bewildering medicinal array: "I take the pill with zebra stripes to cure my early evening gripes. . .This long flat one is what I take if I should die before I wake." Having mastered that challenge, he goes from being "properly pilled" to being "properly billed." Finally, socks, coat and pants restored, necktie back under his chin, he's pleased to assure himself, "You're in pretty good shape for the shape you are in." Seuss, with 82 years and 44 books to his credit, is in better than "pretty good shape"; he's in top form with this book that's sure to delight "obsolete children," and even those of us who are merely obsolescent.