5y 



'Journal of Comparative Neurology and Psychology. 



differences are so slight that no conclusions regarding the advan- 

 tage or disadvantage in growth can be reached. Experiments 

 now in progress will be able to determine this question. 



Owing to the early termination of the experiment, nothing can 

 be said regarding the effect on their longevity. 



When these rats were first weaned and placed in revolving 

 cages their graphic records showed that their activity was more or 

 less distributed over the entire 24 hours of each day. With the 

 exception of the feeding time, when all were active, there was no 

 regularity in their activity. This is easily perceived by consult- 

 ing the graphic record in Fig. 5 which represents 24 hours' activity 

 at the age of 36 days. The interrupted line below indicates the 

 hours as marked by the electric clock. The hne representing the 

 activity of each rat is indicated by the appropriate number at the 

 left. Where the record is a straight line the cage was stationary 



Fig. 5. The graphic record of the activity of each rat at the age of 36 days for a period of 24 

 hours as recorded on the kymograph paper. The broken lines indicate periods of activity, the straight 

 lines periods of rest. 



and the rat was to all appearances resting. Occasionally the 

 interval between revolutions was so great that the individual turns 

 can be made out in the records. But since the kymograph paper 

 moved very slowly — about four inches per hour — the records 

 more often appear as a solid band with occasional interruptions 

 of rest. This record shows the irregularity in the periods of 

 activity. It also shows that the rat is resting much more of the 

 time than it is active. 



In using the term resting I do not w^ish to be interpreted as 

 meaning that the rat was asleep. As a matter of fact immediately 

 after feeding they begin at once to carry their food into the nest 

 boxes. This accounts for the regular and general activity at 

 8 a.m. They no doubt eat this food as they desire during the day. 

 Since the water cannot be carried inside, thev are forced to come 



