(50) Lister was sure that the bacteria were the cause of the wound suppuration, but how did the bacteria get into the wound? One day, Lister made his ward inspections musing over a patient's suppurated wound.

(51) Early in the morning, the soft sun shone into the ward. In the sunlight, Lister saw the dust flying around the room. It struck him that the wound suppuration was due to countless bacteria mixed in the dust contaminated wounds.

(52) Since dust can carry germs, doctors' hands, surgical instruments, and bandages can allbe transmitting media. Following Pasteur's principles of pasteurization, he studied the use of carbonic acid in bacteria sterilizing.

(53) After that, the hospitals became cleaner and more comfortable, and many patients survived without festering wounds. More and more people sought medical help, and some even came across the English Channel.

(54) Lister revolutionized surgery, and his name spread around the world. But he attributed it all to Pasteur. In 1874, he wrote a grateful letter to Pasteur, extolling his inspiration and help.

(55) With carbonic acid sterilization, a new path for medicine was opened. But carbonic acid is a corrosive that both kills bacteria and destroys skin tissue. So people must look for another medicine. This time, the breakthrough was first made in the combat against the smallpox disease.

(56) Smallpox had been a terrible epidemic. For centuries, smallpox would break out almost once a year, and took a large number of people's lives. Those who survived the disease would have many pockmarks left on their faces. People had to pray for God's blessings.

(57) Actually, in the Ming Dynasty in China, our ancestors had employed variolation against smallpox. They used a cotton ball to take some material from scabs of patients sick with a mild attack of the disease, which was then inhaled by persons to be inoculated through the nose. This effective process was called “Human Pox”.

(58) A doctor named Edward Jenner discovered that cowpox can protect against smallpox. Jenner was born in England in 1749. In his early medical learning, Jenner found a woman who had suffered an attack of cowpox before. When the woman was infected with smallpox later, she did not get worse but recovered soon.

(59) “Could it be possible that cowpox was able to prevent smallpox?” Jenner had been pondering for a long time before starting an experiment on May 17, 1796, the day of his 47th birthday.