38 
CURT P. RICHTER 
process of expulsion involves the musculature from the sphyncter 
at the antrum to the sphyncter at the pylorus. Contractions 
begin at the antrum and work downward, one following another 
peristaltically. During the time the process of expulsion is going 
on the part of the stomach above the antrum is engaged in 
macerating and churning the food in acids preparatory to its 
descent below. These processes go on until the stomach is com¬ 
pletely emptied of food. As this process nears completion a new 
group of contractions begin, at first almost imperceptibly, gradu¬ 
ally increasing until finally the musculature of the entire 
stomach is involved. These are the so-called hunger contractions 
(see fig. 20). They occur only when the stomach is empty or 
nearly empty of food. These contractions begin at first at the 
lower end of the pylorus and work downward, each time however 
they begin farther and farther up on the wall of the stomach until 
they involve the entire fundus, and finally the entire stomach right 
up to the carclia. During these contractions marked changes 
take place in the entire organism, changes in blood pressure, 
intra-cranial pressure, reflex excitability, and in the heart-rate, 
while during the digestion contractions no such changes have 
been found to occur. The former contractions give rise to the 
sensations of hunger while the latter are not known to give rise 
to any kind of sensations. 
It is with these hunger contractions that this work will concern 
itself at this point. It was stated above that in the empty 
stomach they come in regular periods at the rate of ten to fourteen 
per twenty-four hours. This rate corresponds very closely with 
the rate of the spontaneous activity periods. The fact of this 
close correspondence in rate may be taken then to indicate 
that these two phenomena occur simultaneously or nearly 
simultaneously. 
Unfortunately it was not possible in the rat to get conclusive 
evidence of the simultaneity of the action of the stomach and the 
spontaneous gross bodily movments. Many attempts were made 
with the balloon method, but the difficulties of the technique due 
to the small size of the animals were too great. A number of 
animals were trained to take a very small stomach tube with a 
