126 L. B. NICE 



In the caffeine line each mouse drank 1 : 300 caffeine citrate 

 solution instead of water, and every other day 3 cc. of 1 :300 caf- 

 feine solution was added to the crackers and milk. 



All of the sixteen mice were given the same food which consisted 

 of buckwheat and oats, every other day crackers and milk, and 

 once or twice a week meat. 



The experiment continued from November 18 to June 8. Dur- 

 ing the winter months the room was heated with hot water and 

 remained at about 65° F. 



To study the spontaneous activity of these mice revolving 

 cages were devised. These cages are similar to those used by 

 Stewart ('98) and later by Slonaker ('07, '12) in their studies on 

 rats. The cages are 6 inches wide by 10 inches in diameter, and 

 made of 8-mesh galvanized wire. Each cage is fastened to an 

 axle which revolves with the cage. The axle is j inch in diam- 

 eter and 18 inches long. The ends of the axle are pointed and 

 set into the end of a bored out set screw forming a pinion which 

 by reducing friction permits the cages to revolve very easily. By 

 means of turning the set screw the pinions can be adjusted in 

 case of wear. The cages are mounted as shown in the accom- 

 panying photograph (fig. 1). 



The revolutions of each cage are recorded by means of an alarm 

 clock whose balance wheel had been removed. A wire about 6 

 inches long is attached to the escapement lever of the clock and 

 to one end of a wooden lever which rests on the axle near one 

 end of a cage. In one brass hub of each cage two pins are set 

 on opposite sides of the axle, and 1^ inches from it. These pins 

 are parallel with the axle. As a cage revolves the end of the 

 wooden lever is raised by each pin in turn causing the clock to 

 register. Each revolution of a cage corresponds to one second 

 on the clock. 



Each cage is supplied with a nest box made of galvanized tin 

 2f inches wide, 2f inches long and 2 inches deep. These are 

 swung to the axle by two wire hooks attached to the top of the 

 nest box near its ends. A tunnel 1| inches square having a wire 

 mesh floor leads to the opening in one end of the nest box where 

 the mouse enters. The floor of the nest box is a hinged door. 



