The Hunger Mechanism in Birds. 



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The hunger mechanism in birds. 

 (Preliminary report.) 



By F. T. Rogers (by invitation). 



[From the Hull Physiological Laboratory of the University of Chicago.] 



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 8H20 con- 

 tractions at intervals of 10-30 minutes. Still later in some birds 

 (probably young) the crop is in a state of almost continuous activ- 

 ity. 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). Each wave requires a time interval of 12 to 15 seconds 

 to complete its cycle. 



This visual evidence justifies the balloon method of recording 

 the contractions. Unless the pressure used is excessive the 

 balloon does not initiate the contractions. 



