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SCIENCE 



[N. S. Vol. XLIII. No. 1122 



method), and photographic apparatus with 

 suitable luminants for registration of the 

 protective wink reflex and of the eye move- 

 ments. Both of the special cameras here 

 used were designed by Dr. Dodge. Many 

 other most ingenious devices for studying 

 the problems arising in the course of the 

 development of the psychological program 

 were made by the experimental skill of Dr. 

 Dodge and will be referred to later. 



DESCRIPTION OP TESTS 



Three fundamental principles determined 

 our selection of the group of experimental 

 measurements : 



First, the attempt to secure a group of 

 systematically coordinated measurements. 



Second, the principle of relative simpli- 

 city, that is, we attempted to investigate 

 elementary neuro-muscular processes in 

 their simplest available form, and of the 

 more complex processes to choose those in- 

 volving as few unknown factors as possible. 

 In particular we tried to measure processes 

 that were insusceptible to direct and arbi- 

 trary conscious modification and as free as 

 possible from uncontrollable influences of 

 bias, effort and attention. 



Third, and finally, we attempted to select 

 those processes in which the motor response 

 of the subject would be a thoroughly nat- 

 ural and familiar act, that is, a customary 

 reaction. 



The effect of alcohol on a relatively 

 simple neural arc, the patellar reflex, has 

 especial significance to clinicians who have 

 long used it for diagnostic purposes. To 

 render its study most capable of accurate 

 scientific interpretation special apparatus 

 was employed for giving the stimulus, and 

 the latency of the response and degree of 

 contraction of the quadriceps muscle was 

 graphically recorded. The stimulus was 

 given by two pendulum hammers of the 

 same weight so placed as to strike the 



tendon. By means of a system of light 

 levers fastening directly over the quadri- 

 ceps muscle, the muscle thickening could 

 be directly recorded on the kymograph and 

 the shock of the impulse blow of the ham- 

 mer made it also possible to record the mo- 

 ment of stimulus. From the moment of 

 stimulus to the beginning of the rise of the 

 curve, the height could be directly read and 

 the extent of the quadriceps thickening 

 could be obtained by noting the height of 

 the curve and applying a simple factor. 



Another simple neural arc which lends 

 itself admirably for study is the protective 

 lid reflex. By projecting a beam of light 

 across the eyelid so that the shadow of an 

 eyelash will fall upon a sensitive plate mov- 

 ing horizontally in a camera, a complete 

 photographic registration showing the mo- 

 ment of stimulus, together with a picture 

 of the lid movement, was obtained. The 

 stimulus was produced by a sounding board 

 struck by two spring hammers, the whole 

 stimulus system having a small pointer whose 

 shadow likewise fell over the camera slit, and 

 thus was simultaneously photographed. As 

 the moving plate was set in motion the stim- 

 ulus hammers were electrically released and 

 the moment of stimulus and the beginning 

 of lid movement, as well as the height of re- 

 sponse, were photographically recorded. It 

 is extraordinarily difficult for a subject to 

 alter the nature of the protective lid reflex 

 or of the knee jerk without this alteration 

 being evident in the records, and we have 

 here, we believe, two indices that give us as 

 nearly uncontaminated data as one could at 

 the present time expect. 



Of the complex neural arcs the movement 

 of the eye to a peripheral visual stimulus 

 is one of the common experiences of every- 

 day life. Consequently, by means of the 

 Dodge photographic registration of the 

 movements of the eye, it was possible to 

 record photographically the time required 



