I This iron lung is now empty for a change. How long it and thousands of others remain j empty depends upon how soon the entire nation is fully vaccinated against polio. i 'Z it " ' ' " 1 " !- -1 N -v'Cy- Almost half the U. S. population pop-ulation is unguarded against crippling polio. Basil O'Connor, president of The National Foundation, has described the vulnerability of some 85 million Americans to paralytic polio as "a national disgrace." There is no scarcity of the Salk vaccine, he pointed out, and two inoculations now, within a month's time, would provide at least some measure ' of protection against polio outbreaks out-breaks and epidemics in the summer. In thousands of cities, villages vil-lages and hamlets across the nation, Salk polio vaccination is avai able at little cost, and in some communities the prescribed pre-scribed series of at least three shots is free. A fourth "booster" "boost-er" shot is now recommended. "The individual's common sense and will to survive should dictate immediate vaccination," vac-cination," Mr. O'Connor said. "If he or she has a family, all the more urgent ground for polio protection." The National Foundation has been joined in its nationwide appeal to the unvaccinated by the American Medical Association Associa-tion and the U.S. Public Health Service. Illustrating vaccination status of the American public, chart shows almost half the population is totally unvaccinated.