copyist's error for nao (腦, "brain") or a graphic loan character for bao (胞, "womb; placenta"). The context describes an ancient method for "coitus with...

U+80Cx 胀 胁 胂 胃 胄 胅 胆 胇 胈 胉 胊 胋 背 胍 胎 胏 U+80Dx 胐 胑 胒 胓 胔 胕 胖 胗 胘 胙 胚 胛 胜 胝 胞 胟 U+80Ex 胠 胡 胢 胣 胤 胥 胦 胧 胨 胩 胪 胫 胬 胭 胮 胯 U+80Fx 胰 胱 胲 胳 胴 胵 胶 胷 胸 胹 胺 胻 胼...

腨 膗 刖 胱 膛 腞 胟 朏 甩 胜 脌 膴 膬 腁 胅 肐 胣 胙 脡 腄 臢 臜 膓 腫 腹 臐 脷 腇 脢 胀 股 肌 肍 朋 朤 鹏 鵬 胞 褜 朐 肳 脗 胸 肑 脆 膽 脃 脕 肷 膖 胮 胳 肒 腶 膄 腉 腴 脠 胕 胉 腺 脾 膇 膍 脽 臇 膲 胏 胝 脂 肵 腯 胻 胍 肜...

practices, and worship of spirits and minor deities: 是非歷臟法、內觀有所思、履行步斗宿、六甲以日辰、陰道厭九一、濁亂弄元胞、食氣鳴腸胃、吐正吸外邪。 This is not the method of passing through the viscera...