An induction shock results in a contraction or fails to do so according to its strength; if it does so at all, it produces in the muscle at that time the maximal contraction that can result from stimuli of any strength.
'Über die Eigentümlichkeiten der Reizbarkeit welche die Muskelfasern des Herzen zeigen', Ber. sächs. Akad. Wiss., Math.-nat Klasse, 1871, 23, 652–689. Trans. Edwin Clarke and C. D. O'Malley, The Human Brain and Spinal Cord (1968)