JOHN WALSH / SCIENCE PHOTO LIBRARY JOHN WALSH / SCIENCE PHOTO LIBRARY
Penicillin. Polarised light micrograph of crystals of the antibiotic drug penicillin. Seen here is penicillin potassium salt crystallized from aqueous solution. The penicillins were the first group of antibiotic drugs to be discovered. Natural penicillins are derived from the mould Penicillium; other penicillin drugs are synthetic preparations. They are used in the treatment of many infections including tonsillitis, pharyn- gitis, bronchitis, pneumonia, the sexually trans- mitted diseases of syphilis and gonorrhoea, and many other bacterial diseases. Magnification: x25 at 35mm size.
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