120 



Scientific Proceedings (74). 



In the crop which contains plenty of food and water a sudden 

 distension of the balloon has little effect. Sudden distension of a 

 balloon in an empty crop initiates a group of contractions. Using 

 too big a balloon or using too much pressure so as to cause excessive 

 dilatation of the crop causes sideways shifting of the neck and 

 crop (shrugging of the shoulders so to speak) evidently an effort 

 on the part of the animal to remove the obstruction. Similar 

 movements may be seen in normal birds which have stuffed them- 

 selves with corn. By mechanical manipulation of the crop with 

 the fingers isolated peristaltic contractions of the crop may be 

 caused. Mere stretching movements of the neck are not sufficient 

 to account for these contractions for they occur when the bird is 

 held quietly in the hand. 



In the normal bird these contractions may be inhibited by 

 external influences such as light and noise. Light and sound do 

 not inhibit them in decerebrate birds but rough handling may do 

 so. Such disturbances of body coordination as those following 

 extirpation of the semicircular canals or lesions of the cerebellum 

 inhibit the contractions of the crop. Incidentally, during the 

 period of marked incoordination following lesions of the semi- 

 circular canals or cerebellum the crop is emptied much more 

 slowly than in normal birds. 



Tonus changes undoubtedly occur but tracings are likely to 

 be deceptive on this point because of the close relation of the crop 

 to the cervical muscles. Any shifting in the position of the head 

 will be registered by the recording balloon in the crop. Hence 

 tracings may be meaningless. But in the hungry bird the crop 

 can be seen to be constricted into a much smaller area. It can 

 hardly be believed that the crop is simply folded and fallen 

 together. (Histological study of the crop distended and empty 

 is being made.) 



A small fistula in the crop does not cause any visible difference 

 in the contractions. The contractions may be inhibited by putting 

 water into the crop through the fistula or by feeding the bird. 

 Water given by mouth does not immediately inhibit the contrac- 

 tions for the peristaltic waves from the throat spread downward 

 over the entire crop. No visible difference can be made out be- 

 tween contractions of the empty crop initiated by swallowing 



