GENETIC TYPE AND THE ENDOCRINES 



533 



reading is based on an increase in air pressure in the closed 

 system. After each reading, the manometer is returned to 

 zero by releasing the pressure. A diagrammatic representa- 

 tion of the saliva recording arrangement is shown in text- 

 figure 85 (fig. 1). 



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Text-figure 85. (1) Diagram of the salivary recording apparatus. (2) Diagram 

 of the apparatus used to produce clicking sounds of variable frequency. (3) 

 Diagram of the shock avoiding apparatus. A string leading from the roller is 

 fastened to the leg of the dog. As the leg is raised the roller is pulled left and 

 breaks the electric circuit to the electrodes. 



Since we were interested in the animals' general mode of 

 behavior rather than in their ability to differentiate between 

 stimuli, highly refined signals were not necessary. The most 

 important factor was that the signal offer a satisfactory 

 stimulus subject to simple control. A telegraph clicker was 

 found to answer these needs. The positive signal in every 

 case was a clicking rate of 120 beats per minute. The negative 

 rates varied from 18 to 98 beats per minute, and in most 

 cases a rate of 50 was used. The clicker sounds were made 

 by a regular telegraph sounder activated by a controlled 



