640 THE POPULAR SCIENCE MONTHLY. 



in one hand and the pencil in the other ; in this way the pencil 

 and the plate sway alike, and no record of it is made. The very 

 fine movements thus obtained are shown in Fig. 4; this figure 

 also shows the slight difference between a record taken by this 

 method Avhile the subject is sitting and while standing, which 

 further proves that the swaying of the body has been eliminated. 

 Traces of periodic oscillations are noted in Fig. \ ; these are due 

 to respiration movements, and in II, of Fig. 5, they are unusually 

 distinct and regular, about twenty to the minute. The forearm 

 of the hand holding the record -plate rests 

 against the body while the recording 

 hand is held free from it, and thus 

 the abdominal movements are 

 recorded. The movements 

 toward the object of 

 attention appear 



Fig. 9. ^-* Counting 

 Metronome. Eecord vertical. 

 Facing <-. Time, 20 seconds. 

 Pencil held in extended right hand. 



throughout. Fig. 5 figures a move- 

 ment toward the rear as well as toward 

 the front ; while Fig. 6 presents a most 

 beautifully regular movement in all four direc- 

 tions. As the metronome, the strokes of which 

 the subject is counting, is carried from one 

 corner of the room to the next, the hand involuntarily follows 

 it and records an almost perfect square. 



It is further interesting to record the movements of the two 

 hands during the same experiment ; a correspondence of move- 

 ment would be attributed to a common swaying of the body, but 

 this would not exclude symmetrical movements of the hands as 

 well. Fig. 7 illustrates the close similarity of the movements : 

 while Fig. 8 shows the importance of the position of the arms in 

 such an experiment. The hand that is held away from the body 

 moves more extensively ; the form of the movement remains simi- 

 lar. All the above records (and Figs. 9, 10, and 14) were obtained 

 upon the same subject ; they are therefore comparable with one 

 another, and illustrate the analysis of the resulting movements 

 into their several factors. 



Involuntary movements are not limited to the horizontal 

 plane ; we may record vertical movements by holding the record- 



