Crossed reflexes of limbs observed in healthy man.

Crossed reflex of limbs has been hitherto observed mainly in decerebrate or spinal animals. In man it was only recognized in pathological cases. The author, however, succeeded in this study in finding a suitable arrangement, in which the crossed reflex involving four limbs could be elicited and recorded even in healthy human subjects. As has been known since the last century, cutaneous stimulation applied to a hind limb of a decerebrate cat reflexively produces, not only contraction of the same hind limb, but also extension of the contralateral hind limb, and further, extension of the ipsilateral paw and contraction of the contralateral paw (Sherrington1898). Strong passive flexion of a hind limb elicits in decerebrate cats reflex extension of the contralateral hind limb (Philippson1905), with further involvement of paws in the reflex (Pi-Surier and Fulton 1928, Samojloff and Kisseloff1928). In healthy humans, crossed reflex of this kind is not shown (Bohme1929), although it appears in central nervous disorders. Schenck and Koehler (1949) recently reported difficulty in detecting the crossed reflex in healthy subjects. Considering the importance of "cross education" (Hellebrandt et al. 1947) in physical rehabilitation, the clarification of the mode of this reflex, especially in humans, may also be of practical value.