Slonaker, Activity of the Rat. 



345 



as being characteristic for the age which they represent. Indi- 

 vidual variation plays an important role, as will be seen later on. 

 The results, however, can in general be considered as fairly typical 

 for the different ages, as later experiments will show. 



The curves in Fig. i indicate the total activity of each rat as 

 represented by the number of revolutions recorded by the clocks. 

 The curves pass through ordinates erected on the base line at 

 points corresponding to the fifth, tenth, sixteenth, twenty-first and 

 the twenty-fifth days of the experiment. As can be readily seen 

 the curves of No. i, No. 2, and No. 4 run fairly close together, 

 while that of No. 3 is very different. The total amount of activity 

 as represented by the number of revolutions is: No. i, 2224; No. 2, 

 2040; No. 3, 10,740; No. 4, 1640. 



table I. 



Average number of revolutions for a period of 24 hours at different ages. 



From this it is not safe to infer that No. 3 represents the age of 

 greatest activity. If this were true, No. 2 would have been a close 

 second, as it was only eleven days younger. It only shows the 

 great individual variation which occurs and must be considered. 



Table I is a tabulation of the average number of revolutions per 

 day on the same days of the experiment as Fig. i. These tabula- 

 tions are plotted as curves in Fig. 2. From these it would appear 

 that No. 3 reached its greatest average daily activity on the six- 

 teenth day of the experiment. It was then 87 days old. After 

 that age the number of daily revolutions steadily decreased. Nos. 

 I and 2 increased slightly. No. 4 shows a gradual decrease from 

 an average of 80 revolutions on the fifth day to 28 on the twenty- 

 fifth day of the experiment. One should not infer that the curves 

 would continue to rise or decline as the case may be had the experi- 

 ment continued. 



