Editing Paul Ehrlich (section)

====In vivo staining====
In 1885 Ehrlich's monograph "The Need of the Organism for Oxygen" (''Das Sauerstoffbedürfnis des Organismus – Eine farbenanalytische Studie'') appeared, which he also submitted as a [[habilitation]] thesis. In it he introduced the new technology of in vivo staining. One of his findings was that pigments can only be easily assimilated by living organisms if they are in granular form. He injected the dyes [[alizarin]] blue and [[indophenol]] blue into laboratory animals and established after their death that various organs had been coloured to different degrees. In organs with high oxygen saturation, indophenol was retained; in organs with medium saturation, indophenol was reduced, but not alizarin blue. And in areas with low oxygen saturation, both pigments were reduced. With this work, Ehrlich also formulated the conviction which guided his research: that all life processes can be traced to processes of [[physical chemistry]] occurring in the cell.