American-Canadian anatomist Robert R. Bensley (1867–1956) and American anatomist Normand Louis Hoerr (1902–1958) disrupted the liver cells in a guinea pig and isolated mitochondria in 1934. Between 1938 and 1946, Albert Claude (1899–1983) continued the work of Bensley and Hoerr and isolated two fractions—a heavier fraction consisting of mitochondria and another fraction of lighter submicroscopic granules, which he called microsomes. Further developments led to the development of centrifugal techniques of cell fractionation commonly used now. The development of this procedure was one of the earliest examples of differential centrifugation. It initiated the era of modern experimental cell biology.