The Contralateral Flexor Reflex, Rebound Phenomena, Co-Contraction and Reciprocal Innervation in Spinal and in Decerebrate Cats

It is generally assumed that the flexor and extensor reflexes are specifically distinct and mutually exclusive. But these reflexes in the legs are not always seen in pure form. Under certain conditions mixed forms occur. Flexor and extensor muscles may contract together either simultaneously or in succession, and it sometimes becomes difficult to draw a sharp line of demarcation between the responses that are primarily flexor and those that are primarily extensor. Furthermore, the rule that ipsolateral stimuli cause flexion and contralateral stimuli cause extension is subject to numerous exceptions. In a previous paper, 1 we mentioned the occurrence of contralateral flexor reflexes, co-contraction and rebound phenomena in the spinal cat. In this paper we shall consider these phenomena in more detail. The literature on spinal reflexes is so voluminous that an adequate review would far exceed the limits of a single paper. Fortunately, several excellent reviews are available (Sherrington,