AVES 



603 



milk" on which the young are nourished. The small intestine is 

 about 60 inches long and is made up of duodenum first, beyond the 

 stomach, and then at the end of the first turn, the ileum begins. It 

 is coiled considerably and leads to the large intestine. The bile 

 ducts coming from the gall bladder and the liver enter the small 

 intestine about fourteen inches below the stomach. The pancreas, 

 which lies beside the duodenum, also pours its contents into the 

 small intestine. Two blind sacs, each about seven and one-half 

 inches in length, and called caeca, extend forward from their point 

 of origin at the juncture of the small and large intestine. They are 

 usually partly filled with a soft, pasty material. The rectum of the 

 large intestine opens into the saccular cloaca. One portion of this 

 space receives the fecal material from the intestine and another 

 portion receives products from the urinogenital organs. The cloaca 

 opens to the outside by the anus. The ileum and caeca serve as the 

 principal organs in which absorption of digested food by the blood 

 occurs. The digestive functions of the bird are very potent and 

 rapid. This seems to be a necessary compensation for the waste 

 caused by their extensive and energetic motions, and their high 

 state of irritability. 



Respiratory System 



The chicken and other birds breathe through the nostrils, nasal 

 chambers, pharynx, superior larynx, trachea, inferior larynx (syrinx), 

 bronchi, bronchial tubes, lungs, and air sacs. 



Air is brought into the nasal chambers through the slitlike nostrils 

 in the upper jaw. Within the nasal chamber the air is warmed by 

 passing over three scroll-like folds which are the turhinated lamina 

 supported by the turlinated hones. Next it passes to the pharynx 

 through a narrow slit in the hard palate. There is a row of filiform 

 papillae or fingerlike projections marking the junction of mouth and 

 pharynx, and another transverse row of horny ones at the juncture 

 of the roof of the larynx and esophageal margin. There is no epi- 

 glottis but simply the slitlike glottis through the anterior wall of the 

 larynx. This is provided with two lips which can be brought tightly 

 together so that nothing can fall through into the larynx when food 

 is being swallowed. From the boxlike superior larynx the air passes 

 through the tubular trachea to the inferior larynx or syrinx where 

 it bifurcates. The walls of the trachea are supported by cartilaginous 



