Editing Paul Ehrlich (section)

====Methylene blue====
[[File:Mundschleimhautzelle.jpg|thumb|Staining ''in vivo'' with [[methylene blue]] of a cell from the mucous membrane of a human mouth]]

In the course of his investigations Ehrlich came across [[methylene blue]], which he regarded as particularly suitable for staining bacteria. Later, Robert Koch also used methylene blue as a dye in his research on the tuberculosis pathogen. In Ehrlich's view, an added benefit was that methylene blue also stained the long appendages of nerve cells, the [[axon]]s. He initiated a doctoral dissertation on the subject, but did not follow up the topic himself. It was the opinion of the neurologist [[Ludwig Edinger]] that Ehrlich had thereby opened up a major new topic in the field of [[neurology]].

After mid-1889, when Ehrlich was unemployed, he privately continued his research on methylene blue. His work on in vivo staining gave him the idea of using it therapeutically. Since the parasite family of ''[[Plasmodiidae]]'' – which includes the [[malaria]] pathogen – can be stained with methylene blue, he thought it could possibly be used in the treatment of malaria. In the case of two patients so treated at the city hospital in Berlin-Moabit, their fever indeed subsided and the malaria plasmodia disappeared from their blood. Ehrlich obtained methylene blue from the company Meister Lucius & Brüning AG (later renamed Hoechst AG), which started a long collaboration with this company.