VALUE OF BIRDS TO MAN. 49 
The Time required for Assimilation of Food. 
If we assume that the stomach and cesophagus of a young 
Crow can contain but an ounce of food, then the bird would 
be required to digest from eight to twelve meals a day, 
according to its appetite and opportunity. The question at 
once arises, How can any digestive system complete such a 
task? Experiments were made with our young Crows to 
determine the time required for 
digestion. The birds were kept 
without food until the stomach 
and intestines were empty. 
They were then fed insects’ eggs, 
in the belief that some parts of 
the shells would escape the grind- 
ing processes of the stomach and 
be voided in the excreta. Sub- 
sequent occurrences justified this 
belief. Ten experiments of this 
kind were made with the two 
birds. Fig. 23.— Young Crows, well 
From the time when the birds iets 
began to feed until the time when the first eggshells were 
dropped in the excreta there elapsed, on the average, one 
hour, twenty-nine minutes and forty-five seconds. The 
shortest time was forty-eight minutes, and the longest one 
hour and fifty-four minutes. This, it should be noted, was 
not merely the time that the food remained in the stomach, 
but the full interval occupied in digesting and assimilating 
it, for within this period at least a part of the food had 
passed the entire digestive tract. 
In most cases all evidence of the food used in the experi- 
ment had disappeared from the excreta in from two to two 
and one-half hours. If we contrast this with the slower 
digestion of man, we shall see how birds readily dispose of 
more meals each day than a man is capable of digesting. To 
learn how long food remains in a Crow’s stomach, it would be 
necessary to kill a large number of Crows, each being killed 
at a longer or shorter interval after it had filled its empty 
