Slonaker, Activity of the Rat. 351 



and 8 in the stationary cages. The experiment was started May 

 9 and stopped July 8, extending over a period of 60 days/ 



The rats were all fed the same kind and approximately the 

 same amount of food each day. The food given to each was not 

 weighed but was measured in a fairly accurate manner. Any 

 slight variation in amount would have no effect because more 

 food was given- than they could eat during the time elapsing before 

 they were fed again. They were fed about 8 o'clock each morn- 

 ing. This consisted in washing the drinking cups, filling with 

 clean water, removing scraps of food not eaten and putting in 

 fresh. An abundance of cracked corn was always provided so 

 that food was always at hand. 



In order to determine the rate of growth each rat w^as weighed 

 at certain intervals during the experiment. Table III indicates 

 the sex, the weights at different ages and the gains. It is readily 

 seen that No. 5 and No. 7 soon surpass the others in weight. It 

 is also noticed that No. 5 is the heavier of the two at the first 

 weighing and that this relationship obtains throughout the experi- 

 ment. These two were males, the other six being females. The 

 females run fairly close in their weights. But here again it is seen 

 that those that were the heaviest at 25 days of age are among the 

 heaviest when the final weights were taken at the age of 85 days. 

 It thus appears that the start which they get while nursing is main- 

 tained. 



Since the males soon surpass the females in weight, they were 

 not taken into consideration in computing the averages. The 

 average of those in the stationary cages is therefore an average of 

 only two. In the revolving cages it is an average of four. 



Table III shows some very interesting results. In the first 

 place, the average weight of those in the revolving cages is greater 

 than the average of the females in the stationary cages both at the 

 beginning and at the end of the experiment. However, at the 

 ages of 45, 56 and 61 days those in the stationary cages surpass 

 the others. At the age of "j^ days they are the same, just what 

 this means one can not say. It is probable, however, that the 

 averages of those in the stationary cages are based on too few 

 individuals and for that reason can not be relied upon. The 



* It was the intention that this experiment should continue throughout the normal life of the rats, 

 but owing to m}' change of residence to California it had to be terminated prematurely. 



