Magneto-electric induction and conservation of force

Verworn (1899) set out how the two kinds of shock differ. In the secondary coil, the making shock follows a slow rise of the primary current, so the electric tension is equalised gradually. The breaking shock equalises very suddenly.¹ For that reason he used only the breaking shock when a very sudden current was wanted on a living object. He graded intensity by the distance between the coils. It was least at greater distance and greatest when the secondary coil was shoved completely over the primary.² In his myograph work, a single moderate shock gave one curve, with a contraction phase and an expansion phase.³

Sherrington (1906) reported that a single induction shock was by itself a subminimal stimulus for the scratch-reflex. In his experience even two shocks failed unless they were very intense and delivered less than 600 a apart.⁴ He still found the summating power of the reflex mechanism great. He also used the word induction for a separate spinal effect between reflexes. Immediate induction occurs only between allied reflexes and tends to fortify the reflex just established.⁵ Pavlov (1927) likewise named a mutual induction of excitation and inhibition, with positive and negative forms.⁹

Jennings (1906) reviewed studies by Roesle (1902) and Statkewitsch (1903) on infusoria. A moderately strong shock usually produced the avoiding reaction, which began with ciliary reversal in the part of the body facing the anode.⁶ Bose (1913) tested a plant with a constant break induction-shock. The shock became ineffective when the stimulated point was cooled. He concluded that lowered temperature depresses excitatory efficiency in the plant's conducting tissue.⁷ Bose (1918) described a fault in his constant-current arrangement. The alternating induction current leaked along the longer circuit and would excite all the leaflets directly. He reported the difficulty as fully overcome.⁸