164 VITALITY AND EFFICIENCY WITH RESTRICTED DIET. 



light on the eye of the subject and at the same instant completed 

 the circuit in the mercury switch, M. 



The sequence of events just preparatory to recording an eye reaction 

 was therefore as follows: 



(1) The operator grasped some one of the cords leading to the stim- 

 ulus device and, by gently pulling, opened a window and held it open. 

 The lamp filaments were glowing red in the box behind the milk glass, 

 but did not give off enough light to make it possible for any subject to 

 discover which window was open. 



(2) The photographic plate was released. Very early in its fall it 

 completed the circuit for the solenoid. The action of this quick and 

 powerful magnet released the frame designated 2 in figure 35. 



(3) The sudden downward movement of the frame and its parts 

 caused the exposure of the e^^e to the 



soft blue photographic light, and at * o o o o 



the same instant the completion of -i. "' 



the short circuit which brought the - *' 

 stimulus light to full brilliancy in the 



opened window. Fig. 34. — Wiring diagram for the eye- 



TWO Other cords shown as C in reaction stimulus apparatus. 



figure 35 were useful in manipulating L, four 60-watt Mazda lamp.? in par- 



,i_ ± /-\ 1.1 allel; R, resistance always in circuit; 



the apparatus. One was connected m, mercury switch for short-drcuit- 



with the shield which temporarily in- i^g R; c, sliding contact; s, solenoid 



terrupted the beam of light from the °^ °^^^^ ^°^ 



subject's eye. This could be drawn down for a moment when focusing 

 and finding position. The other was so arranged that, by pulling on 

 it, the frame 2 could be raised into position after a reaction had been 

 taken and thus made ready for another reaction. This lifting of 2 cut 

 off the light from the subject's eye and broke the circuit to the lamps 

 in the house, H. In the photograph made for figure 35, three of the 

 shutters have been opened so as to expose the light, which can be seen 

 at the points near L in the figure. In the center of the field at which 

 the subject looked there was a white fixation mark which always re- 



EXPLANATION OF FlGTJRE 35. 



B, black screen surrounding subject's field of view; H, lamp house of stimulus apparatus; L, 

 general location of stimulus lights; F, a screen carrying a fixation mark and to be folded down 

 over the plane L when eye movements are photographed ; arrows indicate the path of beam 

 of light; S, a solenoid which, when operated, moves support, /, to left, causing frame, 2, to 

 fall; 2 carries the shield, A, and a part of the mercury switch, M; thus, its fall lights the lamps 

 in H, producing a stimulus at L, and exposes the eye to the recording light; C, two cords, one 

 for lifting 2 again into position, the second for withdrawing A while the camera is focused. 



Explanation of Figure 36. 



Each line of dots is a reaction record. A black dash with one interspace represents 0.01 sec. 

 Counting from the bottom (stimulus) the first definite bend in a line of dots indicates the 

 moment of reaction, e. g., in the extreme left hand record 20 dashes are counted between 

 these points; the reaction time was therefore 0.20 sec. The records are from two subjects; 

 those in the left hand plate show shorter and more regular reactions. 



