Fromation of forward and reverse connections during elaboration of a classical and instrumental acid-defense conditioned reflex

During elaboration of a classical acid defensive conditioned reflex to passive lifting of a foreleg in dogs, the reinforcing stimulus--acid elicited an extension of the leg via backward connection. At the initial stage of elaboration of an instrumental avoidance reflex, the reinforcing stimulus called forth an extension of the leg, whereas at the stage of a stable reflex it produced a flexion.