BEHAVIORISTIC STUDY OF THE RAT 
45 
It must be emphasized that with this 
tentative formulation it is not intended to 
imply that the stomach is the only organ in 
the body upon which spontaneous activity 
may depend. But it is true however that a 
larger part of the activity of the rat does 
fall into these regular clear-cut periods, which 
have been associated with the action of the 
stomach. Besides this activity which falls 
into the regular periods there still remains 
some activity which the limited scope of the 
present work did not permit to be studied 
in detail. Most important here is a rather 
considerable amount of irregular activity of 
females. Whether this irregular activity is 
related to the action of any part of the sexual 
apparatus was not determined. The role 
that the stomach mechanism plays with 
relation to spontaneous activity probably 
varies very greatly in the different species 
of animals. In the lower organisms it must 
undoubtedly account for a very much larger 
part if not all of the spontaneous activity. In 
man, on the other hand, it probably accounts 
for only a limited part of the activity. Still 
the work described above on the relation of 
spontaneous activity to the stomach con¬ 
tractions in humans during sleep would 
indicate that the stomach still plays a very 
important role in bringing about activity 
even in humans, however greatly covered 
over this activity seems to be by the flood 
of reactions elicited by the many different 
external stimuli during waking periods. In 
this connection it would be of importance 
to determine the relation of spontaneous 
activity to the kind and structure of the 
o 
M 
. 21 . Relation of Stomach Contractions to Activity 
