 In the early part of the 20th century he produced the earliest films of mitosis in living cells via "microscopic movies".In 1923 he published an influential textbook on hematology called "Traité technique d'hématologie".Along with American physiologist William Henry Howell (1860-1945), the Howell-Jolly bodies are named; which are 1-2 µm granules seen in erythrocytes (red-blood cells).