BEHAVIORISTIC STUDY OF THE RAT 
43 
a plus of others. The products of this deficiency—whatever they 
are—may be looked upon as the agents which set up the process 
of reestablishing the equilibrium. (This process has for its final 
step the movements of the entire organism about in the environ¬ 
ment until contact with food is made and the food is ingested.) 
As far as is known there is no way for these deficiency products, 
which are probably carried in the blood stream, to stimulate the 
skeletal muscles directly—the muscles which bring about the 
movements of the entire organism. How then is the equilibrium 
reestablished? It is known from direct work on the stomach and 
from analogous work on the heart that the stomach responds to 
chemical stimulation, that its activity may be influenced and 
changed by chemical stimulation. It is safe to assume that these 
deficiency products stimulate the stomach, bring about in it an 
increase in size and rate of the contractions. These contractions 
in turn when they become large enough send impulses to the 
skeletal muscles through the vagi and central nervous system, 
efferent nerves, and release there the stored energy which 
starts the organism in operation of getting food for filling the 
stomach. The fact then that the energy in the muscles is only 
released periodically as was demonstrated above must be ac¬ 
counted for by the periodicity of the action of the stomach. This 
organ is subjected during times when the body is in need of 
nourishment to a continuous stimulation from the deficiency 
stimuli. Progressively as the strength of the stimuli increases 
more and more of the stomach wall responds until the entire 
organ from the cardia to the pylorus becomes involved. After 
a long series of contractions of this kind the musculature finally 
reaches a condition in which suddenly the deficiency stimuli 
are no longer able to elicit a reaction, the contractions cease and 
the stomach becomes quiescent. This quiescent phase which 
follows may be thought of as a period of fatigue in which for the 
time being the muscles are temporarily no longer responsive to 
stimulation. As the muscles recuperate the contractions begin 
again, and progressively as the recuperation process goes on 
they become larger and larger until finally the height of another 
period is reached and the entire reaction is repeated. This 
