38 



PSYCHOLOGICAL EFFECTS OF ALCOHOL. 



MM 



our pendulum bobs were hollow cylinders (C", C", fig. 4), into which 

 closely fitting lead weights, which were accurately adjusted to the 

 desired totals, could be inserted and clamped. In our experiments, 

 the total masses of the bobs were respectively 30, 50, 75, and 100 grams. 

 Magnetic release for the pendulum-percussion hammers provided 

 for accurate timing of the stimuli by means of a circuit-breaker at- 

 tached to the shaft of the kymograph. The magnets which held the 

 hammers (M',M", fig. 4) were attached to a heavy brass arm A. This 

 arm moved on an axis which was 

 coincident with the axis of the 

 pendulums and could be clamped 

 at any desired position on a 

 divided arc C. This provided 

 for considerable latitude of ex- 

 perimental variation in the height 

 of fall and the correlated velocity 

 of the hammer at the moment of 

 stimulation. Except in a few 

 specified cases, our hammers fell 

 from a horizontal to a vertical 

 position, making h in the energy 

 equation equal to the length of 

 the pendulum from its axis to 

 the center of gravity of the bob 

 (20 cm. in our pendulums) . Thus , 

 the energy of the pendulum at 

 the moment of stimulation varied 

 directly with the mass and was 

 respectively 



20X30 e.g. 

 20X50 e.g. 



20X75 e.g. 

 20X100 e.g. 



FIG. 4. 



- A|>j>-u-:i!u* for stiiiuiliitiii-j; tin 1 

 reflex. 



Dodge 1 suggested as an indi- 

 cator of the fatigability of a re- 

 flex, as far as that can be shown 

 in its relative refractory phase, 

 that it would be desirable to give two similar stimuli separated by a 

 definite interval of time within the relative refractory period. For 

 that purpose our pendulum was made double, with similar bobs, and 

 two separate release magnets. The weight of the two bobs was deter- 

 mined directly. The actual lengths of the two pendulums were con- 

 trolled by comparing their periods of oscillation. 



To secure uniformity of application of the two successive stimuli 

 was more difficult. A light wooden rod (B f , fig. 4), about 60 cm. long. 



'Dodge, Am. Journ. Psych., 1913, 24, p. 1. 



