  Here we present an analysis of the paper "Universelle Bedeutung des
Wirkungsquantums" (The universal meaning of the quantum of action), published
by Jun Ishiwara in German in the "Proceedings of Tokyo Mathematico-Physical
Society 8 (1915) 106-116". In his work, Ishiwara, established in the Sendai
University, Japan, proposed - simultaneously with Arnold Sommerfeld, William
Wilson and Niels Bohr in Europe - the phase-space-integral quantization, a rule
that would be incorporated into the old-quantum-theory formalism. The
discussions and analysis render this paper fully accessible to undergraduate
students of physics with elementary knowledge of quantum mechanics.
