154 



PSYCHOLOGICAL EFFECTS OF ALCOHOL. 



with one or more thicknesses of blue glass. The oscillating light- 

 interrupter was set in motion by starting the electrically-driven tuning- 

 fork with which it was in series. The enlarging camera was focused to 

 secure the best image of the arc light as reflected from the cornea of the 

 subject. The shutter dropped and the signal was given to the subject 

 to look from one point of regard to the other, back and forth as rapidly 

 as possible, until the signal to stop was given at the end of 5 seconds. 



A typical record of the eye-movements is reproduced in figure 27. 

 The horizontal lines on this record indicate the moments of visual fixa- 

 tion. The oblique lines of dashes indicate movements of the eye from one 

 fixation point to another. Each sweep is usually continuous until near 

 the end, when a sharp break often occurs, followed by one or more 

 short corrective movements. These corrections are usually not over 

 5 of movement. They are always noted in reading the plates and are 

 recorded in the tables. But their algebraic sums are so nearly constant 

 that no correction of the final values has been attempted on their 

 account. The time interruptions of the record were made by the fork- 

 driven vibrator. The indicate hundredths of a second. Similar time 



FIG. 27. Typical eye-movement record. 



records appear on the original records in the fixation lines, but there was 

 no particular object in adding to the burden of the reading by counting 

 them. Instead, we took the total number of eye-movements in 5 sec- 

 onds to be a satisfactory measure of the fixation pauses. 



RESULTS. 



All our data on the velocity of the eye-movements are collected in 

 table 25, arranged according to the numbers of the subjects. Under 

 movements to the right and left respectively are given the duration of 

 the abductive and adductive eye-movements, together with the extent 

 of the corrective movements. Under the heading "Total movement' 

 is given the sum of the durations of movement to the right and left. 

 This is made the basis of the calculation of the effect of alcohol, in the 

 effort to equalize any fault of muscle-balance that may have been 

 present in any of the subjects, or induced by the experiments. Under 

 "No. of cycles" is entered, as far as data are available, the number of 

 complete cycles of eye-movement and fixation that occurred in 5 

 seconds of experiment. 



