Microorganisms are so small that they can not be seen by the naked eye. A long dish of food will produce some tiny creatures. Sometimes we only know the food is degraded but can not see these little creatures. That is because our eyesight has not reached that level. If the food is placed under a microscope, the results will surprise everyone. Turns out there are thousands of thousands of microorganisms. So how does the microorganism in the food appear?
In fact, in foods that do not have microorganisms, they later grow. Therefore, at first people thought that microorganisms are naturally occurring in food, which is called natural microbial production.
In the 17th century, the biologist of Italy denied this. He did an experiment. Experiment is as follows: in two containers are left to meat, one to open the lid, the other to use a thin cloth sealed. After a while, flies fly into the flask, then the larvae are sprouted, while the flask still does not see flies and worms. Apparently rotting meat can not appear to fly. Flies can only be the result of a previous life. This experiment of Leidy has negated the theory of natural production. But people who hold the opposite opinion say that flies are relatively high animals that can not naturally arise, but does not mean that microorganisms can not naturally arise. In the meantime, the opinions of the two parties have not been resolved.
Soon after, in the eighteenth century. Johnny Niderhan, an early Christian and British biology researcher, also conducted experiments to support the theory of natural birth. He put the lamb juice on fire for 5 minutes, put in a jar and use softwood covered. Theoretically, in this case, microorganisms and flies in the air have no way of getting into the tank, nor can any microorganism grow. But after a few days, the test results are quite the opposite: in lamb juice there are many active microorganisms. So natural birth theory has found new evidence.
It was at this point that a scientist named Lazzaro Spallanzani appeared in Italy. Spallanzani said that Niderhan's defect could appear in this 5-minute heater, if not enough to kill all the microbes in the bottle for 5 minutes, so the results are normal. Therefore, Mr. Spallanzani adapted the method of Niderhan to an experiment, he poured mutton water into the pot, after heating sealed the mouth of the bottle, in which a 5 minute kettle, the pot reheat 1 hour. A few days later, Spallanzani checked, found in a 5-minute boiled water jug filled with microorganisms, and in an hour-heated lamb cavity there was no microorganism any. The incident has been well-documented, but Niderhan countered: "It's hard to keep an hour in the wild, and Spallanzani uses the method. When the heat sealed the jar, afraid that the air in the bottle was pushed out, in a vacuum how microorganisms exist "?
Obviously, Niderhan was irrational, since microorganisms were able to arise naturally, no matter how long the condition of the water had been heated, the problem was that in the vacuum state the experimental results would be same result not. In this case, Spallanzani, when conducting the next experiment, paid particular attention to the fact that when the seal was flushed out so that the air leaked out, the results proved to be exactly the same, so Niderhan finally could not. where to go?
In 1860, the famous French microbiologist and scientist Louis Pasteur designed a more rational experiment. He poured hot boiling water into a long necked and curved heat exchanger, without restricting the air inlet, nor heating the flask, resulting in the presence of microorganisms sticking to the curved portion of the neck, while In the absence of the presence of microorganisms. Obviously, microorganisms penetrate from the air, thus negating the radical nature of the theory.
source: ten thousand questions why? - Animals
p / s: during translation, which uses google translate