NORMAL AND ABNORMAL MOVEMENTS. 



129 



In Plate 556 farther interesting details of this case are illus- 

 trated. 



If Mr. C. is sitting quietly in a chair, with the arm in the 

 semiflexed position already described, and then lies down with 

 his back and head flat upon the ground, all vibration in the hand 

 ceases. It becomes perfectly quiet, and he can execute with it 

 most exact and delicate voluntary movements. If, however, he 

 now attempts to raise the head, violent tremor at once appears in 



Fig. 22. 



the hand. (See Fig. 22.) This tremor is so violent that the feet 

 and head are aifected. It is remarkable that raising of the head 

 is the only movement that provokes the tremor. Raising the 

 right hand or either foot has no effect. 



Fig. 23. 



Similarly, if Mr. C lie upon the ground and the motion be 

 completely arrested, it is again violently excited by striking the 

 patellar tendon (see Fig. 23, and series second of Plate 556) or by 

 attempting to elicit ankle clonus. 



The duration of exposure for each individual picture was less than .004 

 second. The sum total of the nine intervals and ten exposures is (.43 -|- .04 = 

 .47) equal to .47 of a second. In series B, Plate 557, six positions complete the 

 movement. 



