432 



ANIMAL BIOCHEMISTRY 



Tongue — -y^. 



Lower mandible 



Opening to trachea — Vh />i .. , • . „• 

 J'i -J-— Muscles controlling 



Opening into gullet- — ^\.\ tongue 



Spleen 



Glandular stomach 



Gall-bladder 

 Bile duct 



Gizzard 



Y \ -Rectum 

 ' -^^ ■ '^^ Cloaca 



\ /-*^;~PT~Anus. 



\ .J- 



■^ 



-Duodenal loop 

 -Caecum 



FIGURE 17-3. Sliowing various portions of the digestive tract of the domestic fowl. 



(After Lippiiicott.) 



period considerable gastric digestion takes place. The finely ground 

 contents are then passed on to the small intestine. 



INTESTINAL DIGESTION 



The pyloric sphincter opens Irom lime to time in response to the 

 semifluid stomach contents of low pH presented by the peristaltic 

 waves of the pylortis. As soon as sufficient of the material called chyme 

 passes through the sphincter to lower the pH at the intestinal wall, 

 the pyloric sphincter closes. It thus admits chyme in intermittent 

 small portions and prevents overloading of the intestine and an exces- 

 sive acidity. Meanwhile gastric digestion continues and the stomach 

 acts as a storage organ, allowing the animal to eat occasional large 



