born Dec. 29, 1863, Basel, Switz.
died Nov. 10, 1934, Wiesental
Swiss cardiologist.
His father, Wilhelm His (1831–1904), first realized that each nerve fibre stems from a single neuron and invented the microtome, a device used to slice thin tissue sections for microscopic examination. The younger His discovered (1893) the specialized muscle fibres (bundle of His) running along the septum between the heart's left and right chambers. He found that they help communicate a single rhythm of contraction to all parts of the heart, and he was one of the first to recognize that the heartbeat originates in individual cells of heart muscle.