The hunger mechanism in birds. (Preliminary report.)

Both normal and decerebrate pigeons have been used in this study. Hunger is marked by the appearance of restlessness. This restlessness appears before the crop is completely empty. Lack of water even though the crop be distended with dry food is marked by restlessness of the bird. These things are true of birds with cerebrum intact, partially, or wholly removed.

During hunger, changes occur in the behavior of the crop. In the normal bird with “appetite”(?) satisfied or at least in the bird which does not of its own accord eat of an abundant food supply, the crop is very much distended. In this condition only occasional contractions of the organ can be detected by means of a rubber balloon; none are visible to the eye (after removal of the feathers over the crop). An hour or two after feeding there begins to appear in the crop contractions in groups of three or four at intervals of 15-20 minutes. The activity of the crop is gradually augmented and 8-12 hours later there occur groups of 8-20 contractions at intervals of 10-30 minutes. Still later in some birds (probably young) the crop is in a state of almost continuous activity. When the content of the crop has been lessened to about one third of its capacity these contractions are directly visible. At this time they may be seen to involve principally the lower part of the crop. When it is completely empty these contractions are periodic in groups of 8-16 occurring at intervals of 10-60 minutes. Each contraction may be seen to begin at the upper part of the crop and sweep as a deep constriction, preceded by a marked bulging or relaxation, over the entire crop (and probably down to the gizzard).