BEHAVIORISTIC STUDY OF THE RAT 
5 
met by means of the construction of small triangular shaped wire 
cages large enough to permit the animals to move about freely. 
A photograph of one of these cages is shown in figure 1. This 
cage is 10 inches high and each side is 14 inches long. It has an 
aluminum bottom fastened to the cage. The bottom is sup¬ 
ported under each corner on a rubber membrane stretched 
tightly over a large tambour. The tambours are connected 
together immediately under the cage into one tube which is led to 
a small Marey tambour, the lever of which records on the smoked 
Fig. 1. Activity Cage 
paper of a kymograph. By this means every movement of the 
animal, even the slightest, is recorded on the drum with a single 
mark. The cage and support are rigid enough to prevent any 
stimulation arising from shaking of the cage or from insecurity 
of foot-hold. 
The attack on this problem of the spontaneous gross bodily 
activity of the rat was begun with the simple experiment of 
observing what happens to the activity when the animals are 
placed in a situation described above free from all external 
stimulation in constant complete darkness. A typical record 
