Slonaker, Activity of the Rat. 



343 



cage and its accessory parts for obtaining and transmitting a cer- 

 tain kind of action; second, the recording apparatus composed of 

 a clock which accurately records the number of revolutions made, 

 and the writing lever and kymograph which graphically show the 

 distribution of the activity during the day and night. As each 

 rat is in a separate cage and each cage has its own recording clock 

 and writing lever these records may be directly compared at any time. 



Revolutions 

 lOOOO _ 



4000 _ 



2000 _ 



Days 



i'lG. I. Curves representing the total activity of each rat as indicated by the number of revolutions 

 recorded by the clocks. 



All the experiments were carried on in a large basement room 

 facing the north and west. Frosted windows furnished a subdued 

 and almost uniform light during the daytime. At night street 

 lights cast in a very dim light, but this was not sufficient to enable 

 a person to avoid coming in contact with obstacles when entering 

 the room. The temperature was fairly constant during the day 

 and varied between 6o° and 70° F. At night it was much cooler 

 but never lower than 40°, even in extreme cold weather. 



