344 'Journal of Comparative Neurology and Psychology. 



The rats were fed and watered about 8 a.m. each day. At this 

 time the clocks recording the number of revolutions were read. 

 They were also read late in the afternoon between 5 and 6 o'clock. 

 In this manner the activity for daytime and night time was easily 

 ascertained. Further details will be described in the discussion of 

 the different experiments. 



Revolutions 

 600 



40o . 



500 , 



2o0 . 



100 



Pays 5 10 15 20 25 



Fig. 2. Curves of the average number of revolutions of each rat per day based on the data in Table I. 



EXPERIMENT I. 



For Experiment I four healthy rats of different ages were 

 selected. Their ages at the beginning of the experiment were as 

 follows: No. I, 30 days; No. 2, 60 days; No. 3, 71 days; No. 4, 266 

 days. Rats of different ages were taken in order to ascertain at 

 once whether there was any marked difference in activity due to a 

 discrepancy in age. The experiment lasted 25 days, beginning 

 February i and ending February 25. 



The curves of Figs, i and 2 and the tabulations in Tables I 

 and II show the condensed results of the experiment. While 

 these show a great difference, they cannot be wholly relied upon 



