" READ THE PASSAGE GIVEN BELOW AND ANSWER THE QUESTIONS THAT FOLLOW: DESPITE ALL THE RESEARCH, EACH ONE OF US CATCHES COLD AND MOST OF US CATCH IT FREQUENTLY. OUR FAILURE TO CONTROL ONE OF THE COMMONEST OF ALL AILMENTS, SOMETIMES SEEMS RIDICULOUS. MEDICAL SCIENCE REGULARLY PRACTICES TRANSPLANT SURGERY AND HAS RID MANY A COUNTRIES OF SUCH KILLING DISEASES AS TYPHUS AND THE PLAGUE. BUT THE PROBLEM OF COMMON COLD, IS UNUSUALLY DIFFICULT AND MUCH IS YET TO BE DONE TO SOLVE IT. IT IS KNOWN THAT A COLD IS CAUSED BY ONE OF A NUMBER OF VIRAL INFECTIONS THAT AFFECT THE LINING OF THE NOSE AND OTHER PASSAGE LEADING TO THE LUNGS BUT THE CONFUSING VARIETY OF VIRUSES MAKES STUDY AND REMEDY VERY DIFFICULT. IT WAS SHOWN IN 1960 THAT MANY TYPICAL COLDS IN ADULTS ARE CAUSED BY ONE OR THE OTHER OF A FAMILY OF VIRUSES KNOWN AS RHINOVIRUSES, YET THERE STILL REMAIN MANY COLDS FOR WHICH NO VIRUS HAS YET BEEN ISOLATED. THERE IS ALSO THE DIFFICULTY THAT BECAUSE THEY ARE SO MUCH SMALLER, THAN THE BACTERIA, WHICH CAUSES MANY OTHER INFECTIONS, VIRUSES CANNOT BE SEEN WITH ORDINARY MICROSCOPES. NOR CAN THEY BE CULTIVATED EASILY IN THE BACTERIOLOGISTS LABORATORY, SINCE THEY ONLY GROW WITHIN THE LIVING CELLS OF ANIMALS OR PLANTS. AN IMPORTANT RECENT STEP FORWARD, HOWEVER, IS THE DEVELOPMENT OF THE TECHNIQUE OF TISSUE CULTURE, IN WHICH BITS OF ANIMAL TISSUE ARE ENABLED AND TO MULTIPLY INDEPENDENTLY OF THE BODY. THIS HAS GREATLY AIDED VIRUS RESEARCH AND HAS LED TO THE DISCOVERY OF A LARGE NUMBER OF VIRUSES. THEIR ^EXISTENCE HAD PREVIOUSLY BEEN NOT ONLY UNKNOWN BUT EVEN UNSUSPECTED. . THE FACT THAT WE CAN CATCH COLD REPEATEDLY CREATES ANOTHER DIFFICULTY. USUALLY A VIRUS STRIKES ONLY ONCE AND LEAVES THE VICTIM IMMUNE TO FURTHER ATTACKS. STILL WE DO NOT GAIN IMMUNITY FROM COLDS. WHY ? IT MAY POSSIBLY BE DUE TO THE FACT THAT WHILE OTHER VIRUSES GET INTO THE BLOODSTREAM WHERE ANTIBODIES CAN OPPOSE THEM — THE VIRUSES CAUSING COLD ATTACK CELLS ONLY ON THE SURFACE. OR IT MAY BE THAT IMMUNITY FROM ONE OF THE MANY DIFFERENT VIRUSES DOES NOT GUARANTEE PROTECTION FROM ALL OTHERS. IT SEEMS, THEREFORE, THAT WE ARE LIKELY TO HAVE TO SUFFER COLDS FOR SOME TIME YET. ON THE BASIS OF YOUR READING OF THE ABOVE PASSAGE, MAKE NOTES ON IT IN POINTS ONLY, USING ABBREVIATIONS WHEREVER NECESSARY. ALSO SUGGEST A SUITABLE TITLE. "