potentiometric measurements and the cellular membrane. In 1926, he moved to Johns Hopkins University in Baltimore as resident lecturer in medical research and in 1929 to the Rockefeller Institute of Medical Research in New York City, where he retired in 1941. The Michaelis-Menten equation Michaelis's work with Menten led to the Michaelis–Menten equation. This is now available in English. for a steady-state rate in terms of the substrate concentration and constants and (written with modern symbols). Classification of Inhibition types Michaelis was one of the first to study enzyme inhibition, and to classify inhibition types as competitive or non-competitive. In competitive inhibition the apparent value of is increased, and in non-competitive inhibition the apparent value of is decreased. Nowadays we consider the apparent value of to be decreased in competitive inhibition, with no effect on the apparent value of : Michaelis's competitive inhibitors are still competitive inhibitors by this definition. However, non-competitive inhibition by his criterion is very rare, but mixed inhibition, with effects on the apparent values of both and is important. Some authors call this non-competitive inhibition, but it is not non-competitive inhibition as understood by Michaelis. The remaining important kind of inhibition, uncompetitive inhibition, in which the apparent value of is decreased with no effect on the apparent value of , was not considered by Michaelis. Fuller discussion can be found elsewhere. Hydrogen ion concentration Michaelis built virtually immediately on Sørensen's 1909 introduction of the pH scale with a study of the effect of hydrogen ion concentration on invertase, and he became the leading world expert on pH and buffers. His book was the major reference on the subject for decades. Quinones In his later career he worked extensively on quinones, and discovered Janus green as a supravital stain for mitochondria and the Michaelis–Gutmann body in urinary tract infections (1902). He found that thioglycolic acid could dissolve keratin, a discovery that would come to have several implications in the cosmetic industry, including the permanent wave ("perm"). A full discussion of his life and contributions to biochemistry may be consulted for more information. "Catalysing" the Suzuki method of music teaching During his time in Japan Michaelis knew the young Shinichi Suzuki, later famous for the Suzuki method of teaching the violin and other instruments. Suzuki asked his advice about whether he should become a professional violinist. Perhaps more honest than tactful, Michaelis advised him to take up teaching,