Kuniomi Ishimori and the first discovery of sleep-inducing substances in the brain.

Experimental studies of the extraction of substances from the brain capable of inducing normal sleep, until its establishment in the 1980s, are reviewed. Although it is believed that Legendre and Pieron induced sleep in dogs by injecting substances extracted from the brains of sleep-deprived dogs (1910-1913) and that Pappenheimer et al. (1975) extracted a sleep-inducing powder from the brains of sleep-deprived goats, the first person to actually attempt the extraction of sleep-inducing substances from the brain of sleep-deprived dogs was Kuniomi Ishimori, a Japanese physiologist. He reported his experimental results in 1909. The contents of his data and an outline of his study are introduced briefly. His original paper has been translated into English and is given in an Appendix.