The improbable chain of events that leads Alexander Fleming 1. ______ to discover penicillin in 1928 is the stuff which scientific myths 2. ______ are made. It was a discovery that would change the course of the history. The active ingredient in that mold, which Fleming named penicillin, turned to be an infection-fighting agent of 3. ______ enormous potency. When it was finally recognized as what it was--the efficacious life-saving drug in the world--penicillin 4. ______ would alter forever the treatment of bacterial infections. By the middle of the century, Fleming’s discovery spawned a huge phar- 5. ______ maceutical industry, churning out synthetic penicillin that would conquer some of man-kind’s most ancient scourges, including syphilis, gangrene, and tuberculosis. When he died a heart attack in 1955, he was mourned by 6. ______ the world and buried as a national hero in the crypt of St. Paul’s Cathedral in London. Although Fleming’s scientific work in and of itself may not have reached great, his singular contribution 7. ______ changed the practice of medicine. He deserves our utmost recog- nition. At the same time, we must bear on mind that the 8. ______ "Fleming Myth", as he called it, embodies the accomplishments of many giants of anti-biotic development. Fleming is but a cho- sen representative for the likes of Florey, Chain, Domagk, and Waksman, many of who remain, sadly, virtual unknowns. 9. ______ Their achievements have made the world a better, healthier place. In commemorating Fleming, and we commemorate them 10. ______ all. How does it happen that children learn their mother tongue so well When we compare with adults learning a foreign 11. ______ language, we often find this interesting fact. A little child without knowledge or experience often succeeds to a complete 12. ______ master of the language. A grown-up person with fully developed 13. ______ mental powers, in most cases, may end up in a faulty and inex- 14. ______ act command. What accounts of this difference 15. ______ Despite other explanations, the real answer in my opinion lies partly with the child himself, partly in the behavior of the 16. ______ people surround him. In the first place, the time of learning the 17. ______ mother tongue is the most favorably of all, namely, the first 18. ______ years of life. A child hears it speak from morning till night and, 19. ______ what is more important, always in its genuine form, with the right pronunciation, right intonation, right use of words and right structure. He drinks all the words and expressions which come to 20. ______ him in a fresh，ever-bubbling spring．There is no resistance： there is perfect assimilation．