Medical scientist, surgeon. Born into the Yamaguchi family, physicians serving a daimyo. He was mentored by Taizen Sato in 1842 and learned Dutch surgery. He was adopted by Taizen and in 1854, he took over as the head of the family and became the second principal of Juntendo. He was mentored by Pompe van Meerdervoort. He became an excellent surgeon and Pompe wrote about him in his book "Nihon Taizai Kenbun-ki" (Vijf jaren in Japan). In 1873 he opened a private hospital, Juntendo, in Shitaya.