128 



A STUDY OF SOME 



arrows in Fig. 20, which, like Fig. 19, is the result of superim- 

 posed tracings of the individual pictures. The arm extended, 

 and the hand and fingers contracted, describe a circle in front of 

 the body. Tlie hand sweeps upward and inward, passes the face, 

 sweeps upward and outward, then downward, and then inward 

 again to its original position. 



At the same time that this spasm of the left arm is taking 

 place the right arm, too, becomes convulsed. ( Vide Fig. 20.) It 

 is raised abruptly, and the forearm directed upward, and a series 

 of to-and-fro movements commence, and which examination shows 

 are synchronous with the rotary movement of the opposite limb. 

 As the rotating limb rises, the right arm rises ; as the former de- 

 scends, the latter descends. As the left arm sweeps inward and 

 upward, the right arm steadily ascends ; as the left arm goes out- 

 ward and downward, the right arm steadily descends. There is 

 certainly here a curious association of movement. 



If, instead of raising the arm to the shoulder, Mr. C. simply 

 sharply flexes the left forearm at the time 

 it is rotating, as in Fig. 21, a series of 

 to-aud-fro movements replace the rotary 

 movements. (J^de third series, Plate 

 557, and Fig. 21.) That is, the left arm 

 is thrown violently backward and for- 

 ward. At the same time the right arm 

 becomes similarly affected, and it, too, is 

 thrown violently backward and forward. 

 As in the previous experiment, the move- 

 ments are found to be synchronous. 



It will be observed that at no time 

 does the right hand become contracted 

 and the fingers " clawed." 



Some idea may be gained of the rapid- 

 ity of these movements when we reflect 

 that the complete cycle of the movement represented in Fig. 1 9 occu- 

 pied less than .47 part of a second, while in Fig. 20 the rapidity had 

 so much increased that the cycle occupied only .32 of a second.* 



Fig. 21. 



* The intervals of time between the positions of the upper series of Plate 

 557 were .048 of a second. The entire movement is included in ten pictures. 



