VALUE OF BIRDS TO MAN. 



41 



refuse is voided. This is digestion . The food is often manip- 

 ulated, crushed, or divided by the beak. It then receives 

 saliva from the inouth, and passes through the phar3'nx into 

 either the gullet (a muscular and membranous tube) or crop 

 (a pouch) , as the case may be, organs capable 

 of great distention, and connecting with the 

 first division of the stomach. Here, then, 

 is the first receptacle of the food. Birds 

 of prey. Herons and some other large birds 

 sometimes fill the gullet to the very mouth, 

 while awaiting the digestion of the food in 

 a stomach already full. The Pelicans have 

 also another great receptacle or pouch, ex- 

 ternal and beneath the beak, where a store 

 of food can be carried. Many of the smaller 

 birds also are able, after filling the stomach, 

 to stow away a still larger supply of food 

 in the gullet. The stomach is large, and 

 usually capable, by distention, of contain- 

 ing a considerable quantity of food. The 

 food passes from the gullet or the crop to 

 the proventriculus or glandular portion of 

 the stomach. This is where the process 

 of digestion begins. Mixed with salivary, 

 ingluvial, and proventricular secretions, the 

 food next passes to the gizzard or muscular 

 division of the stomach, where the food grist is ground fine. 



Among seed-eating birds the heavy, powerful muscles of 

 this portion of the stomach are, with the rough, calloused 

 stomach lining, assisted in their work by sand and gravel 

 Avhich are swallowed. This mineral matter takes the place 

 of teeth in grinding the food. 



In vegetable-feeding birds the intestine is very long and 

 much coiled, while the digestive tract is generally shorter 

 and simpler in the flesh-eating and fish-eating species. All 

 the processes of digestion are remarkably rapid. The sali- 

 vary o-lands, the liver and the pancreas all quickly pour their 

 copious secretions into the alimentary canal ; the food is 

 chylified after impregnation with the biliary and pancreatic 



Fig. 17. — Alimen- 

 tary c.inal of Blue- 

 bird, reduced ; after 

 Audubon, a, 6, gul- 

 let or oesophagus ; c, 

 proventriculus ; d, 

 gizzard ; e, f, h, in- 

 testine ; i, cloaca. 



