ACTIVITY OF THE ALBINO RAT 23 



In connection with their activity it was very easy to deter- 

 mine the rate of growth and final decline due to old age. Care- 

 ful weighings were taken at sufficient intervals to indicate this. 



DISTRIBUTION OF THE DAILY ACTIVITY 



The young were taken from their mothers when they were 

 28 days old. They were carefully weighed and placed in their 

 individual cages as has already been noted. Hereafter they 

 will be designated by the numeral given each. 



When first introduced into its cage each rat showed a marked 

 degree of curiosity. It examined every corner and object within 

 the inclosure, using mainly the sense of smell assisted by the 

 sense of touch and to a still less degree that of sight. After 

 about an hour of such investigation most of those in the revolv- 

 ing cages had found their way to the nest boxes in which they 

 remained for a time. The graphic record of their activity (Fig. 

 1) shows that their periods of activity and rest were numerous. 

 The activity would consist of a few turns of the cage then rest 

 soon to be followed by another short run. In only a few cases 

 did an individual keep up the activity longer than a few minute s 

 at a time. At this age the periods of activity were not confined 

 to any special part of the day, but were rather uniformly 

 distributed throughout the 24 hours. Coupled with this activity 

 manifested in running was that accompanying investigation by 

 the animal as already noted. After a few days, however, they 

 became familiar with their surroundings and appeared to be 

 perfectly at home. Their activity then was characterized by 

 their running. At intervals they would frisk and jump about 

 in play, a characteristic of most young animals. As they grew 

 older this playfulness became gradually less and less and was 

 replaced by more uniform and regular running. 



By consulting Figs. 1-10, which are graphic records of the 



Figure 1. Graphic record as recorded by the kymograph of the activity when 

 the rats were 32 days old and 4 days after they had been weaned and placed 

 in the revolving cages. 



Figure 2. Graphic record of activity at the age of 6 months. 



Figure 3. Graphic record of activity at the age of 11 months. 



Figure 4. Graphic record of activity at the age of 16 months. 



Figure 5. Graphic record of activity at the age of 21 months. 



Figure 6. Graphic record of activity at the age of 25 months. 



Figure 7. Graphic record of activity at the age of 26 months. 



Figure 8. Graphic record of activity at the age of 28 months. 



Figure 9. Graphic record of activity at the age of 31 months. 



Figure 10. Graphic record of activity at the age of 34 months. 



