Engelmann , Theodor Wilhelm

(1843–1909) German physiologist

Engelmann, the son of a publisher, was educated at Jena, Heidelberg, and Göttingen, before obtaining his PhD from the university in his native city of Leipzig in 1867. He immediately joined the faculty of the University of Utrecht, serving there as professor of physiology from 1888 until 1897 when he returned to Germany to a similar chair at the University of Berlin, where he remained until his retirement in 1908.

Between 1873 and 1895 Engelmann published a number of papers on muscle contraction. By this time, following the work of such physiologists as William Bowman, the main anatomical details of striated muscle had been established. However an explanation was needed as to why the anisotropic or A bands refract polarized light quite differently to the isotropic or I bands. Engelmann had noted that in contraction the A bands increased in volume while the I bands decreased. He consequently proposed his ‘imbibition’ theory in which the contraction of striped muscle is attributed to a flow of fluid from the I to the A bands.

Engelmann also worked on the nature and mechanism of the heartbeat and in 1875 devised an experiment that proved the heartbeat is myogenic; that is, the contraction originates in the heart muscle and not from an external nerve stimulus. In 1881 he discovered the chemotactic response of certain bacteria to oxygen, and he also demonstrated that red and blue light is far more effective in stimulating plant chloroplasts during photosynthesis than other parts of the spectrum.