446 



KNIGHT DUNLAP 



of the usual house lighting circuits) , lamp resistance or a rheostat 

 may be used to control the current ; or a rectifier of the proper 

 type may be used without resistance. The scheme with resist- 

 ance is shown in figure 2. The standard four-receptacle voltage- 

 reducing lamp board (lamp board no. 1) is here represented, but 



LAMP BOARD No.l 



STIMULUS LAMPS 



ELELCTRIC FORK 

 Z5 or 50 Vibrations 



FIG. 1. CHRONOSCOPE OPERATED ON DIRECT CURRENT; THROUGH TUNING-FORK 



INTERRUPTER 



Set up for visual discrimination reaction utilizing same current source. 



