The collection includes the manuscripts of lectures that Yukawa gave in the meetings and colloquia held in the Department of Physics and the meetings of the Physico-Mathematical Society of Japan during the period of 1934 to 1935. Yukawa recognized clearly before anyone else that quantum mechanics would serve as the foundation for all domains of physics. To his fellow physicists, Yukawa described in detail that quantum mechanics was very important in explaining not only nuclear physics such as beta decay and the Dirac sea but also characteristics (properties) of metals and crystals, as well as in statistical mechanics. He also mentioned that for ordinary people, the world described by modern physics was close to the common-sense world people perceive. Yukawa conducted research, taught students and raised people’s awareness of physics with a sense of mission, and that is very impressive and inspiring.