0308 托福试题阅读（ 55minutes ）Question 1 -11If food is allowed to stand for some time, it putrefies .When the putrefied materialis examined microscopically ,it is found to be teeming with bacteria. Where do thesebacteria come from , since they are not seen in fresh food? Even until the mid -nineteenthcentury, many people believed that such microorganisms originated by spontaneous(5 ) generation ,a hypothetical process by which living organisms develop from nonlivingmatter.spontaneous the of theory of The most powerful opponent Louis and microbiologist chemist generation was the French Pasteur(1822 -1895).Pasteur showed that structurespresent in air closely resemble the microorganisms seen in putrefying materials .He didthis by passing air through guncotton filters, the fibers of which (10)stop solid particles. After the guncotton was dissolved in a mixture of alcohol and ether, the particles that it had trapped fell to the bottom of the liquid and were examined on a microscope slide .Pasteur found that in ordinary air these exists a variety of solid structures ranging in size from 0.01 mm to more than 1.0 mm .Many of these bodies resembled the reproductive tructures of common molds, single -celled animals, and various s(15) other microbial cells .As many as 20 to 30 of them were found in fifteen liters of ordinary air ,and they couldlarger much found the distinguished not be from organisms in the .Pasteur putrefying in numbers materials concluded that organisms found in putrefying materials originatedfrom the organized bodies present in the air .He postulated that1these bodies are constantly(20)being deposited on all objects.Pasteur showed that if a nutrient solution was sealed in a glass flask and hea...
