STUDIES IN THE PHYSIOLOGY OF THE NERVOUS SYSTEM. XIX.: THE SUCCESSIVE EFFECTS OF THE COMPOUNDING OF REFLEXES IN THE “DE‐AFFERENTED” CONDITION—DECEREBRATE PREPARATIONS

1. In the present paper the successive effects of the synchronous compounding of reflexes are examined in the “de‐afferented” state of the decerebrate preparation. 2. Where the two antagonistic stimuli are synchronously withdrawn it has been observed that a flexor rebound contraction may appear on their withdrawal even where it is seen in neither “pure” reflex. 3. Where the ipsilateral flexion‐reflex is made to interrupt the contralateral extension‐reflex (“background”), and the extension‐reflex is continued after the withdrawal of the interrupting ipsilateral stimulus, complete restitution of extensor contraction has been observed in the third phase of the compound reaction—that is, in the phase in which the extension‐reflex still continues after the withdrawal of the interrupting ipsilateral stimulus. This was observed to be the case even where there was a “flexor rebound contraction after excitation” in the “pure” ipsilateral flexion‐reflex. Where the extension “background” was varied in strength it was found that the restitution was the more complete the stronger that “background” was. It was not observed to be augmented above the level of extensor contraction in the “pure” extension‐reflex. 4. In these same circumstances a flexor rebound contraction may appear on the withdrawal of the “background” extension‐reflex even where it is not present in the “pure” reaction. In series of compound reactions in which the time relations of the interrupting and background stimuli are changed this flexor rebound contraction has been found to be of greater extent the later the ipsilateral interrupting stimulus falls in the period of the extension “background” stimulus—that is, the shorter the period of the third phase of the compound reaction. 5. Where the abnormal ipsilateral response of extension occurs in reply to weak stimuli (but the normal flexion in response to stronger ones) it has been found that during double stimulation there may occur extension augmentation and that a further augmentation may occur in the third phase of the compound reaction. 6. Where the “background” is one of ipsilateral flexion and the interrupting stimulus is the contralateral the reactions have been examined both when extensor rebound contraction and when flexor rebound contraction have been present. 7. In cases in which “extensor rebound contraction after excitation” occurs in the “pure” extension‐reflex there may occur a corresponding phenomenon in the third phase of the compound phenomenon. This may disappear when a greater strength of ipsilateral “background” stimulation is used. Where extensor rebound contraction occurs in the “pure” flexion‐reflex that may be found to be augmented in the compound reaction when the flexion “background” is withdrawn. Sometimes the withdrawal of the “pure” ipsilateral stimulus may be followed first by a “flexor rebound contraction after excitation,” and then by an extensor rebound contraction. In such cases it may be found that the primary flexor rebound contraction is augmented on withdrawal of the ipsilateral “background” stimulus in the compound reaction and that there is a similar augmentation of the secondary extensor rebound contraction. The duration of the primary flexor rebound contraction in the compound reaction is of less duration than that in the “pure” reflex, although its extent is greater. 8. In cases in which flexor rebound contractions are present in the “pure” extension‐reflex and flexion‐reflex it is found that in the third phase of the compound reaction there is an augmented restitution of flexor contraction. This often has the form of the flexor rebound contraction of the “pure” extension‐reflex, but it may be of much greater extent and may even appear when the strength of contralateral stimulation is subliminal. Where the ipsilateral “background” stimulus is subliminal the flexor contraction of the third phase is of greater extent and duration than the flexor rebound contraction of the “pure” extension‐reflex. In the compound reactions it is greater the stronger the subliminal ipsilateral stimulus. With supraliminal stimuli it is found that the flexor augmentation of the third phase is greater the stronger either stimulus is when the other is kept of constant value. In the fourth phase of the compound reaction “flexor rebound contraction after excitation” may occur, and is then found to be of greater extent than is the same phenomenon in the corresponding “pure” flexion‐reflex. 9. The successive effects of the compounding of reflexes in as far as they have been examined in the “de‐afferented” condition appear to be similar to those which have been found to occur in the “normal” state of the decerebrate preparation.