CHARACTERISTICS OF ACTIVITY .Q 



The remaining figures (7, 8, 9 and 10) represent the records for 

 the ages twenty-six, twenty-eight, thirty-one and thirty-four months-re- 

 spectively. No. 4 in Figure 7 shows the death struggle of this rat, which 

 ended a Httle before 10 p.m. 



In comparing these dififerent records of activity, one notices that 

 in the young rats the periods of activity and rest are of short duration 

 and have no definite arrangement so far as the time of the day is con- 

 cerned. As the rats grow older the activity becomes greater and 

 occurs more and more during the night time, the periods of rest being 

 confined to the daytime. This continues until the rats reach the prime 

 of life. After some months of almost uniform activity there is a grad- 

 ual reduction, and the distribution and amount of work done approaches 

 that of youth. It also shows that the vegetarians are not as active, that 

 they age more early, and that their duration of life is shorter than the 

 omnivorous rats. 



Since all the animals were fed on a mixed diet for twenty-eight 

 days after commencing the experiment, any difiference in activity dur- 

 ing this period must be considered due to individual variation. This 

 variation is sometimes very noticeable, as seen in Table I. This table 

 represents the average number of revolutions of five consecutive days 

 of each rat at the ages indicated. There is not a gradual and regular 

 increase in the amount of running done by each, but fluctuations — now 

 greater, now less. At first this was thought to be due to making the 

 average from too small a number of days. Therefore another table 

 (Table II) was made, by taking the average run of each sex of each 

 group for a whole month. The figures in the column of the omni- 

 vorous males thus represent the average of thirty days' run of three 

 individuals. But here again we see the lack of a uniform increase. In 

 other words, the activity manifests itself rhythmically. No doubt if 

 the number of individuals had been greater the results would have been 

 more uniform. In a former paper I have discussed the causes of these 

 fluctuations.^ 



Table II is put in the form of curves in Figure 11. The rhythmical 

 variations are very conspicuous. These fluctuations also correspond in 

 many cases both in regard to time and appearance. For example, from 

 the beginning to the third month there is a rapid rise in the curves, 

 showing a great increase in the daily activity. This was, no doubt, due 

 to the feed, for they were all fed on a strong mixed diet for almost a 

 month, and on rich food for almost two months. The effect of this 

 food carried them over apparently till the end of the third month, when 

 they began to feel the effects of the lack of it. This was followed in a 

 general reduction of amount of daily activity in all except the omnivorous 



