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Walter Hesse

Walter Hesse is best known for his work in microbiology, specifically his work in developing Agar as a medium for culturing microorganisms.

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Hesse joined Robert Koch's laboratory (effectively in a post-doctoral position) to study air quality. Hesse was convinced that microorganisms were presesnt everywhere, even in the air. He used a series of filters, made mainly from wadding, in attempts to capture and observe microorganisms.

When culturing the organisms he trapped with his filter, he used a gelatin-containing medium capable of solidifying. Frustratingly, the medium had a tendency to melt during the summer months, thus ruining the experiments. Additionally, many of the organisms he cultured were capable of degrading the gelatin meduim, also ruining his experiments.

Legend has it that Hesse went on a picnic with his wife (Angelina Fannie Hesse) and noticed that the jellies and puddings that she had brought along did not melt in the hot summer weather. When asked why this was so, Lina (as she was called) replied that they contained Agar, and that she had been shown the trick by a Dutch neighbor (recently emigrated from Java (Indonesia) when she was growing up.

Further development of agar showed that it would not easily melt (though would remain molten at lower temperatures once it did), was not easily degraded by microorganisms and was a flexible medium.