Hydrogen ion Concentration. Its Significance in the Biological Sciences and the Methosds for Its Determination‐By leonor Michaelis, M. D. Professor in the University of Berlin, Resident Lecturer in Research Medicine in the Johns Hopkins University. Volume I, Principles of the Theory, represents the authorized translation from the second revised and enlarged German edition by William A. Perlzweig, Ph.D. of Johns Hopkins University and Hospital. Cloth bound, 6 × 9, publishers, The williams & Wilkins Company, Baltimore, Md. Price $5.00