Rubner thinks man cannot live on meat alone.
Rubner, M., in von Leyden, E., Handbuch der Ernghrungstherapie, Leipsic, 1,42 (1903)
Rubner called attention to the fact that a man cannot live on meat alone because of the physical limitation of the apparatus of mastication. He was evidently considering only lean meat as fat offers little difficulty. via