江戸時代と聞くと、武士や町人文化の華やかさがまず思い浮かぶかもしれないが、その一方で、当時の人々は自然の法則を探求し、生活を豊かにするための科学技術や、人々の命を救うための医学の分野でも、地道ながらも着実な発展を遂げていたんだ。「鎖国」という限られた国際環境の中でも、日本独自の知恵と、わずかな窓から入ってくる西洋の知識とが融合し、ユニークな成果を生み出していった。
【学術的豆知識】平賀源内 – 江戸のレオナルド・ダ・ヴィンチ？
江戸時代中期の化政文化期に先駆けて活躍した人物に、平賀源内（ひらがげんない）(1728-1780)がいる。彼は讃岐高松藩出身の武士だが、その才能は実に多岐にわたっていた。本草学者として物産会を開き、蘭学者としてエレキテル（摩擦起電機）を復元し、寒暖計や火浣布（石綿の布）を製作。さらに、戯作者として浄瑠璃や洒落本を書き、洋風画を描き、鉱山開発にも手を出すなど、まさに「江戸のレオナルド・ダ・ヴィンチ」とも呼べるような万能の才人だった。彼の活動は、当時の日本が持っていた知的好奇心の旺盛さと、新しいものを取り入れようとするエネルギーを象徴している。しかし、そのあまりに時代を先取りした才能と奔放な性格は、時に周囲との摩擦を生み、晩年は不遇だったとも言われているんだ。
(Click to listen) Hiraga Gennai (1728-1780), active before the Kasei cultural period in the mid-Edo era, was a truly multifaceted talent, often dubbed the "Leonardo da Vinci of Edo." Originally a samurai from Takamatsu Domain in Sanuki, his genius spanned numerous fields. As a herbalist, he organized product fairs; as a Rangaku scholar, he replicated an "Erekiteru" (electrostatic generator) and produced thermometers and asbestos cloth (kakanpu). Furthermore, he wrote Jōruri and Sharebon as a Gesaku writer, painted Western-style pictures, and even ventured into mine development. His activities symbolize the vibrant intellectual curiosity and the energy to embrace novelty that existed in Japan at the time. However, his talents, too far ahead of his time, and his uninhibited personality sometimes caused friction with those around him, and it is said his later years were unfortunate.
This Page's Summary in English (Click to expand and listen to paragraphs)
This page explores the development of science, technology, and medicine during the Edo period. Despite Japan's "sakoku" (national seclusion) policy, indigenous advancements were made, and Western knowledge was selectively absorbed, primarily through Dutch Learning (Rangaku).
Wasan (Japanese mathematics) flourished independently, characterized by practical applications (surveying, commerce) and a highly sophisticated, almost recreational, aspect (e.g., "idai keishō" problem-solving challenges, "sangaku" votive tablets with math problems). Seki Kōwa is a towering figure, establishing algebraic methods (tenzanjutsu) and achieving world-class results in areas like pi calculation and determinants. Yoshida Mitsuyoshi's "Jinkōki" greatly popularized wasan.
Calendrical studies (Rekigaku) and astronomy (Tenmongaku) were vital state concerns. Shibukawa Harumi created the Jōkyō calendar (1685), Japan's first domestically produced lunisolar calendar based on actual observations, replacing the long-used Chinese Senmyō calendar. Later, the Kansei calendar, incorporating Western astronomical knowledge, was developed by scholars like Takahashi Yoshitoki. The Shogunate's Astronomical Observatory (Tenmonkata) was responsible for these tasks. Inō Tadataka, under Takahashi's tutelage, conducted a nationwide survey and created the remarkably accurate "Dai Nihon Enkai Yochi Zenzu" map of Japan.
Honzōgaku (herbalism and natural history), influenced by Chinese materia medica, developed with figures like Kaibara Ekiken ("Yamato Honzō," "Yōjōkun") and Ono Ranzan, who empirically studied and classified Japan's flora and fauna. Public interest in natural history grew, with product fairs and illustrated encyclopedias.
Medicine (Igaku) saw the coexistence and interaction of traditional Sino-Japanese medicine (Kanpō) and newly introduced Western medicine (Ranpō igaku). Within Kanpō, the Koho-ha (Ancient Method School), advocating a return to classical Chinese medical texts and emphasizing empirical observation, emerged (e.g., Yamawaki Tōyō, who performed Japan's first documented human dissection). Ranpō igaku, primarily through Dutch sources, significantly impacted surgery and anatomy. The translation of the Dutch anatomical atlas "Ontleedkundige Tafelen" as "Kaitai Shinsho" (1774) by Sugita Gempaku and Maeno Ryōtaku was a landmark event, promoting an empirical approach. Hanaoka Seishū developed general anesthesia ("Tsūsensan") for surgery, and Ogata Kōan championed smallpox vaccination. These advancements contributed to improving medical standards and laid some groundwork for Japan's later modernization in science and technology.
これで「文化編」の探求は全て終了だ。学問・思想、元禄・化政の町人文化、そして科学技術・医学の発展と、江戸時代の知と美、そして技の世界を旅してきた。
次は、いよいよ江戸時代の最終章、「江戸時代の終焉」へと進むぞ。
