Ehrlich

“The study of oxygen uptake became the basis of Ehrlich’s 1885 Habilitation . . . Das Sauerstoff-Bedürniss des Organismus [The Requirement of the Organism for Oxygen]. In this, Ehrlich showed that dyes were transported to the cells in the blood stream as fine particles, in which form they entered the cells. Then, held in environments in which they were sensitive to protoplasmic consumption of oxygen, they underwent reduction [became colorless]. This was manifest as color changes. Thus Ehrlich made maximal use of dyestuff properties by observing the in vivo reduction of colorants with different oxidation-reduction potentials. The infusion of knowledge from a technological pursuit into a scientific discipline was even more apparent in the 1885 dissertation than it was in earlier studies. . . . Ehrlich’s in vivo experimental approach to the study of oxygen uptake by observing color changes in dyes” (Travis II, 395-396).