The Reflex Mechanism of the Insect Leg

1. Variations in the frequency of the motor discharges to the leg muscles of Periplaneta americana are followed in the intact animal under different types of sensory stimulation by electrical recording from the muscles. 2. Two main reflexes are described: the depressor reflex, evoked by stimulation of the campaniform sensilla on the legs, and a levator response to touch on the upper side of the leg. 3. There is a direct antagonism in the excitation of the depressor and levator sets of muscles: also between similar muscles in the two legs of a segment. 4. Reflex effects are not transmitted up or down the animal to other segments. 5. The conditions for the reflex excitation of the two types of motor fibre are discussed. 6. A suggestion is put forward for the explanation of rhythmic movements.