CHAPTER V. 



DisiiASEs oe THE Alimentary Tract. 



The arrangement of the digestive organs in birds differs from 

 that in other domestic animals in that the mastication of the 

 food does not take place in the mouth. The food of birds, con- 

 sisting mainly of grains and seeds, is swallowed whole into the 

 crop. It remains here until it is completely softened by the 

 juices secreted by this organ. The food then passes into the 

 stomach (proventriculus) where it is mixed with still other 

 juices, and then into the gizzard. The muscular walls of the 

 gizzard grind the softened food against the small pebbles (grit) 

 which the bird picks up, until it becomes a paste. This paste is 

 then passed into the intestines and mixed with the secretions 

 from the liver, pancreas and the intestines themselves. The 

 nutritive elements of the food are transferred through the intes- 

 tinal walls, by means of the activity of the cells composing these 

 walls, into the blood and are carried to various parts of the 

 animal to be used in building up the tissues. 



In the wild state birds are forced to hunt for their own food. 

 They go about gathering in a few seeds here and there but 

 probably at no time is the crop overloaded. Under conditions 

 of domestication the birds are fed only once or twice a day and 

 thus the crop is often gorged with a day's supply of food. 

 Further the lack of sufficient grit, lack of exercise and the feed- 

 ing of rich, soft mashes cause the birds to be predisposed to- 

 wards indigestion. Under these conditions poultry are subject 

 to a large number of disorders of the digestive system. 



DISEASES OE THE CROP. 



Impacted Crop (Crop Bound). 



In general two immediate causes may be given for birds be- 

 coming crop bound. ( i ) The thin muscular walls may be para- 

 lyzed either through over-distention with dry grain or through 

 some disease, as cholera and diphtheria. (2) The opening into 



