Размещено 5 лет назад по предмету Английский язык от olechka199812

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The antibiotic action of green mould, from which penicillin was subsequently obtained, was first discovered by the Russian physicians V.A. Manasscin and A.G. Polotebnov as far back as the 70's of last century. They not only established that mould retards the growth of microbes, but also successfully treated various kinds of ulcers with compresses for which mould was used. Although these Russian scientists were unable to extract the active element, penicillin, from the mould, owing to the low level of technical development their time, their discovery to a great measure paved the way for the subsequent use of penicillin as a therapeutic agent.

Thirty-five years later V.G. Tanakovsky, a Russian veterinary, published a paper on the results of his experiments which showed that a certain form of mould killed the microbe causing typhus. This expanded still further the range of microorganisms known to science whose vital activities are inhibited by substances produced by mould.

It is a self-evident fact that no science can develop without a sound theory summarizing and explaining its practical achievement. The science of antibiotics owes its developments first and foremost to the researches of Ily a Mechnikov, the outstanding Russian biologists, who discovered that certain types of bacteria arc dislodged by other in the intestines of both man and animals. The scientist gave an explanation of this highly interesting phenomenon. What happens is obviously a struggle among microbes with some species producing toxins that arc lethal to others. Working in the beginning of this century, Mechnikov was the first scientist to prove theoretically that it is possible to use the struggle among microbes in the interests of man.

Mechnikov, rightly called by his contemporaries “the great humanist”, devoted much effort to the problem of combating premature aging of the human organism. Man he said, is the victim of constant poisoning by toxic substances produces in his own intestines. It is here, in the digestive tract, that the enemies of the organism, putrefaction bacteria, constantly produce strong toxins which bring about premature old aee. But how is the harmful flora to be expelled from the organism? Could it not be done with the help of the micro-organisms themselves, by making use of the struggle going on among them? Mechnicov began to search for bacteria harmless to
man which, on being introduced into the intestines, could drive out the putrefaction microbes.
Investigations established that lactic bacteria, which cause the souring of milk, answer the purpose. In their presence putrefaction bacteria perish.
Mechnicov’s assistant, the Russian scientist Ignat Schiller, succeeded in proving this in practice.
Me found a medium in which lactic bacteria grew rapidly. This was lactose. He only had to feed mice with lactose and their intestines became populated with a pure culture of lactic bacteria. Experiments on man (lactose is perfectly harmless) confirmed that under the influence of sugar these bacteria as a rule drove out the putrefaction microbes from the intestines.