STUDIES IN THE PHYSIOLOGY OF THE NERVOUS SYSTEM. VII.: MOVEMENTS UNDER NARCOSIS IN THE PIGEON. MOVEMENTS UNDER NARCOSIS IN THE RABBIT‐PROGRESSION — SCRATCHING — FLEXION

1. The pigeon exhibits peculiar rhythmic movements in some cases while in the state of narcosis. These movements are seen as bilaterally symmetrical flexion of the hind limbs, depression of the tail, and flapping of the wings. The wing movements commence with rapid flapping—these members being in a state of extension and abduction—and are then succeeded by a state in which the flapping is replaced by a state of flexion and adduction. This movement is bilaterally symmetrical; it is rhythmic—the manifestations of the phenomenon being separated by intervals of rest; and it is probably connected with the normal movements of flight. 2. Three different types of movement may occur in the rabbit when in a state of narcosis. 3. Of these the first is the hop. The hind limbs describe rhythmic movements which are bilaterally symmetrical. There is flexion at all three joints, succeeded by extension. The movements of the hind limbs are simultaneous, and the rhythm lies between 1·2 and 2·0 beats per second. Records of the movements of the isolated quadriceps extensor cruris demonstrate active movement synchronous with the hopping movements in the limbs. These contractions are commonly separated by short intervals of rest at the level of relaxation. 4. The second type of movement to occur in the rabbit is the scratch. In its main features this phenomenon corresponds very closely with the similar phenomenon already described as taking place in the guinea‐pig. Peculiarly well marked in the case of the rabbit are the movements of the head and neck, face, and ears. Analysis of the movements of the scratch shews that the “beats” are of irregular form and rhythm. This variation of rhythm may lie between 0·75 and 4·5 beats per second. The differences in the form and rhythm of the beats may be due to the complication of the movements of the scratch with concurrent hopping movements. 5. The third type of movement exhibited by the hind limbs may be described as a simple act of flexion. Here the one hind limb performs a short movement of flexion. There is no maintenance of the flexion, and during its exhibition the contralateral hind limb performs a synchronous act of extension. The flexions occur usually upon the one side only at any one time. They may occur in groups, but then appear to have no rhythmic relationship. When they occur close together there is a summation of the “residual flexion” which is present in each single act. 6. The three types of movement in the rabbit may be compounded in different combinations during the phenomena seen under narcosis. The movements of the scratch may be preceded by the movements either of progression or of flexion. In the former case the hopping movements are abolished at the point of initiation of the scratch in the hind limb which goes into extension. But the other hind limb sometimes shews the persistence of the hopping movements superposed upon the maintained flexion of the scratch. In this case the maintained flexion may commence as a very slow rise. The flexion movements in a similar manner may precede the movements of the scratch. In this case the flexion is seen upon the same side as that upon which the scratching first appears. Two or three flexion movements may be grouped together. These shew the summation of the “residual flexion,” and finally there is complete mergence with the maintained flexion of the scratch, which then appears as at its full extent.