8 EFFECT OF DIET ON THE ALBINO RAT 



ACTIVITY. 



In studying the characteristics of the activity one needs to refer 

 to the kymograph records. Figures i to lo inclusive are reproductions 

 of such records, and show the activity of each rat for twenty-four con- 

 secutive hours at different ages. By comparing these figures a great 

 difference is noticed in the activity at different ages. 



Figure i represents the activity of each rat at the age of thirty- 

 two days, and just four days after they had been weaned and placed in 

 the revolving cages. There is no regularity in the distribution of the 

 activity and periods of rest. Neither is there any apparent tendency 

 to be more active at one time in the twenty-four hours than at another. 

 They were restless, playful and filled with a spirit of investigation. 

 Since they were all fed at this time on the same diet, any differences in 

 the character of the activity may be attributed to individual variation. 



In Figure 2, which shows the distribution of the activity at the 

 age of six months, two important things are noticed. First, the great 

 bulk of the activity occurs during the evening and early night time; 

 second, the omnivorous rats (O) are more active than the vegetarians 

 (V). There is more or less random running for an hour or so before 

 and after the feeding time (4 p.m.), but the most is done during the 

 night. 



At the age of eleven months (Figure 3) the periods of activity and 

 rest are more sharply defined. Also the difference in the amount of vol- 

 untary activity of the two classes is very obvious. The activity of the 

 vegetarians is approaching closely in appearance that of old age.^ 



In Figure 4 the activity at the age of sixteen months is seen. 

 Some days previous to this record the feeding time was changed to 

 the morning to see what effect it would have on the distribution of the 

 activity. The main bulk is seen to remain constant, but the usual ran- 

 dom running which occurs at the feeding time has shifted to the morn- 

 ing. At this age two of the vegetarians have died and the other two 

 compare very unfavorably with the work of the omnivorous. 



Figure 5, which represents the activity at the age of twenty-one 

 months, shows that when the feeding time is returned to the afternoon 

 the periods of activity and rest are sharply defined. The omnivorous 

 feeders are still quite active when compared to the remaining vege- 

 tarians. 



At the age of twenty-five months all the vegetarians were dead 

 (Figure 6). The records of the omnivorous rats show a marked ten- 

 dency toward old age. Especially is this true in No. i and No. 4. 



