(40) Back to the laboratory, Loeffler scraped the white substance from the sick child's throat, made it into solution and then injected a rabbit's larynx on it. He waited for twelve hours, and then another twelve, but the rabbit just hopped around lively with ears erected.

(41) This kind of bacteria may not be the killer? Loeffler hesitated for a while but he chose to wait with patience, bearing his fatigue. Another twelve hours went by, the rabbit finally had difficulty breathing. It struggled but died on the ground.

(42) As Loeffler cut the rabbit's larynx open, he discovered the same tunica albuginea in its narrow throat. Putting it under the microscope, he saw the matchstick-shaped bacteria again! Yes, there it was. He found the pathogen of diphtheria. It was the killer bacteria!

(43) Ignoring his fatigue, Loeffler dashed out of the laboratory and shared his excitement with others. This type of bacteria, discovered by Loeffler, is called Diphtheria Bacillus, which releases a powerful toxin that paralyzes one's heart and kills human beings.

(44) Loeffler's discovery promoted more extensive research on pathogens. A lot of germs were later found one after another. In 1883, a cholera epidemic raged Egypt and took the lives of groups of infected patients. The whole Egypt was in grave condition.

(45) When the news reached Europe, Koch and his students rushed over there. They worked day and night despite the hot sun and the scorching heat, and finally discovered Vibrio cholerae in a patient's enteric cavity.

(46) It was then that Koch's student Louis contracted Cholera and passed away soon. For the health of human beings, scientists have paid a heavy price in the battle to find pathogens.

(47) Thousands of types of bacteria have been discovered, but not all of them are harmful. It is the pathogenic ones that cause disease. After the identification of enemy pathogen came the battle against it, which first took place in a hospital named the Edinburgh Royal Infirmary.

(48) In the 18th century, when medicine was just emerging from the clutches of witch doctors, hospitals were messy, filthy, and death rates were high. Only Dr Joseph Lister's Edinburgh Hospital in Britain was clean, comfortable and had a low mortality rate.

(49) But post-operative suppuration of wounds in the hospital was still very serious, threatening the patients' lives. Lister was so concerned that he pored over Pasteur's writings, studying the theory of bacterial putrefaction.