82 PSYCHOLOGICAL EFFECTS OF ALCOHOL. 



in characteristic corrective movements of the eye. Nevertheless, the 

 possibility of anticipatory reactions is unfortunate. They tend to 

 increase the variability of the results, even though the records clearly 

 show their existence. Moreover, it is not always easy to distinguish a 

 corrective movement which follows a guess from the normal corrective 

 movement which follows inadequate coordination of the eye-muscles. 

 A further objection, which will appear in the discussion of the results, 

 is the surprisingly large effect of repetition. It would probably be 

 better, in the future, to instruct the subject to keep his eye on a fixa- 

 tion mark, and then move the fixation mark in one direction or another 

 as a stimulus to reaction. 



TIME RECORDS. 



As in our measurements of the lid reflex, time records are incor- 

 porated directly into the record of the position of the eye by interrupting 

 the recording beam of light with the vibrator in series with an electric- 

 ally driven tuning-fork of 50 d. v. per second, as described on page 60. 

 The records taken in this manner are a series of dashes. Each dash 

 represents 0.01". 



EXPERIMENTAL PROCEDURE. 



With the subject seated in position 2, with the vibrator and its con- 

 trolling tuning-fork in operation and the arc light burning steadily, 

 the subject was instructed to assume the position for eye-reaction. 

 The subject then pressed his head gently against the head-rest, which 

 had been adjusted to the proper elevation. The operator inserted the 

 sensitive plate and focused the camera. Before each series began, the 

 operator repeated the standard instruction, " Look at the fixation mark, 

 and read the letters as soon as they appear. Don't try to guess where 

 they will come." About one second after the signal, " Ready," was 

 given, the photographic plate was released and the shutter was dropped. 

 The dropping shutter carried with it the prefixation mark, exposed the 

 letter, and simultaneously permitted the recording beam of blue light 

 to reach the eye. After reaction the shutter was raised and the expo- 

 sure apparatus w r as reset by an assistant. The operator raised the 

 photographic plate, moved the camera a few millimeters to the left, and 

 repeated the experiment. Five records were made in succession in 

 each period. All five can easily be recorded on the same plate without 

 danger of interference or fogging the plate. At the end of the day's 

 work the plates were unloaded, dated, and numbered. The assistant 

 who read the plates numbered the curves in the order of the experi- 

 ments, counted the dashes, and noted the corrective movements. 



Figure 12 reproduces an illustrative photographic plate containing 

 five records of eye-reactions. Each line of dashes represents an eye- 

 reaction. The beginning of each line is coincident with the exposure of 

 the stimulus to move the eyes. The reaction movement of the eyes is 



