28 Effect of Alcohol on Psycho-Physiological Functions. 



of each day, another series for period 2, and so on. In the Dodge and 

 Benedict experiments the series was exposed three times to the subject, 

 but in the repetition experiments only two complete exposures were 

 used, as mentioned, in order to reduce the possibility of the words pre- 

 sented being completely learned by the subject and remembered from 

 day to day. 



(8) Eye reaction to peripherally appearing stimuli. — A slight move- 

 ment of the subject's chair brought him into position for this measure- 

 ment and the two which follow. The sudden fall of a shutter carrying 

 a fixation mark exposed another mark or letter, which was 1, 2, or 3 

 cm. to the right or left of the aforesaid mark; the distance of the object 

 from the eye was 48 cm. The subject, who was in ignorance of the 

 exact place where the stimulus mark would appear, was instructed to 

 look from the fixation mark to the stimulus as soon as it should appear 

 to him, and to pronounce the letter aloud if it were a letter that was 

 exposed. A beam of light, interrupted by a tuning fork and of com- 

 fortable intensity, was made by reflection to fall upon the eye at the 

 moment of appearance of the stimulus. From the cornea this light 

 was reflected through an enlarging camera and registered itself on a 

 falling photographic plate. The resulting string of dots with the sharp 

 bend at the moment the eye moved to the exposed letter or mark is a 

 record from which the reaction time can be easily and accurately 

 counted. Five such reaction records were taken side by side on the 

 same plate. 



(9) Eye movements. — The general apparatus in this measurement 

 was the same as that which was used for the eye reactions. At the 

 instant that the interrupted light was turned upon the eye a dot ap- 

 peared, this time in an expected position. From this the subject looked 

 40° on his arc of vision to the left to a second dot, and then back to the 

 first, and continued these movements as rapidly as possible throughout 

 the period of 5 seconds during which the photographic plate was falling. 

 In the records each dash with one interspace represents 0.01 second. 

 Precautions were taken to guard against head movements by the use of 

 a suitable head-rest. The left eye was covered with an opaque screen. 

 Uniform instructions preceding each record were to make the move- 

 ments as fast as possible, but to look carefully at the fixation marks. 

 With this particular subject, t^hese instructions should have been re- 

 versed and strong emphasis placed on the careful fixation of the marks 

 in their turns. 



(10) Protective lid reflex. — An artificial eyelash consisting of a strip 

 of black paper 1 by 16 mm. was attached to the left lid so that it re- 

 mained in a horizontal position when the eye was open and viewing a 

 fixation mark. This could be worn without discomfort for an indefi- 

 nite period, except possibly when the subject rubbed his face with his 

 hand. When a beam of interrupted light was reflected across the face, 



