INFLUENCE OF INTERNAL FACTORS 151 
but eventually become weaker and may later be replaced by 
movements of rejection. That it is not the mere filling of the 
digestive cavity alone that determines the change of be- 
havior is shown in an experiment of Jennings on Aiptasia, 
in which the digestive cavity was filled with filter-paper. 
When so filled that pieces of paper were repeatedly disgorged 
the anemones continued to take in new pieces. The meta- 
bolic conditions of the organism are therefore a determining 
factor in its behavior toward food. 
To a certain extent though, the food taking is influenced 
by the previous local stimulations of particular parts of the 
body. Nagel and Parker have found in Adamsia and 
Metridium that the tentacles of a certain part of the body 
after being stimulated several times with filter-paper soaked 
in meat juice will refuse to carry it toward the mouth. If 
now the soaked paper is offered to other tentacles they give 
the usual food taking reaction. Similar behavior in Aipta- 
sia was observed by Jennings, who found also that if one set 
of tentacles had carried several pieces of meat to the mouth 
until they refused to carry it longer, the other tentacles, 
while they might still carry the meat, would cease to respond 
much sooner than they would if the animal had not already 
received food. The animal according to Jennings “is a 
unit so far as hunger and satiety are concerned.” 
The effects of hunger and satiety on the behavior of higher 
forms are so general and so familiar that we need not pursue 
the subject further. As regards food animals in general are 
self regulating mechanisms, and if under certain conditions 
an injurious quantity of food is devoured, or material which 
is unwholesome is selected, the exceptional behavior only 
serves to emphasize the rule that the food taking of animals 
is on the whole pretty adequately adjusted to their needs. 
In higher forms this function is conscious and voluntary, 
