26 
CURT P. RICHTER 
very easily as was demonstrated by the fact that 30-gram rats 
were able to turn them as many as 12,000 times in twelve hours. 
A photograph of the drums is shown in figure 13. Six such 
drums were used in this experiment. 
By placing the animals in the drums alternately every six hours 
it was possible to take records on twelve animals at one time. 
Six animals were always running in the cages while the other six 
rested in small separate stationary cages. In this way each 
animal spent twelve out of every twenty-four hours in the drums. 
Fig. 13 . Photograph of Revolving Drum 
The animals used in this experiment were of six different ages, 
30, 100, 210, 250, 450 and 600 days. Records were taken con¬ 
tinuously for one month with the exception of an occasional da} r 
of rest. Only the scores made during the last twelve days of the 
experiment are included in the final record for the reason that all 
of the animals showed very great irregularities during the first 
part of the month while they were adapting themselves to the 
drums. A curve based on data obtained in this way is shown in 
figure 14 in which the age of the animals in days is given on the 
abscissae, and the number of complete revolutions per day are 
given on the ordinates. 
