328 D. I. MACHT, S. ISAACS AND J. GREENBERG 



dose of antipyrin administered by him to his subjects was 1 gram 

 or 15 grains; whereas the ordinary therapeutic dose of that drug 

 employed at present is a quarter of a gram or about 4 grains. 

 In the present investigation, the doses of all the drugs employed 

 were therapeutic doses. 



METHOD 



The method of investigation was the same as that followed in 

 the opium experiments. 



The reaction time was measured by means of an improved 

 chronoscope devised by Prof. Knight Dunlap, which is a far more 

 accurate and convenient instrument than the old Hipp instru- 

 ment. The apparatus is described by Professor Dunlap else- 

 where (3). It consists essentially of a synchronous motor, run 

 on a tuning fork vibrating fifty times per second, and registering 

 the time in units of 2o- or 1/500 of a second, the dial-hand of the 

 chronoscope being controlled by an electro-magnetic clutch. 



The simple sound reaction was obtained by the experimenter 

 calling out a word or number into the speaking disc which started 

 the chronoscope and the subject responding with a set answer as 

 soon as possible through another speaking disc, thus stopping the 

 clock. The results were then recorded in terms of 2o- or 1/500 of 

 a second. It is needless to state that the subject and experi- 

 menter were separated by a curtain in order to prevent their 

 seeing each other. 



The simple touch reaction was obtained in a similar manner. 

 The experimenter touched the hand of the subject behind a cur- 

 tain, the pressure of the touch starting the chronoscope going. 

 The subject responded as soon as he perceived the touch sen- 

 sation by pressing a bulb or touching a key which immediately 

 stopped the clock. 



The simple light reflex was tested by the experimenter's press- 

 ing a key and thus lighting an incandescent lamp behind a white 

 screen, the subject responding by pressing another key which 

 extinguished the light and stopped the chronoscope. 



In order to determine the more complex reaction time or asso- 

 ciation reaction time, various devices were tried, such as response 

 to certain words (nouns and adjective, subject and predicate, 



