EXERCISE 85 



pharynx- 



HOW THE ANIMAL DIGESTS ITS FOOD 



Statement. Just as the plant is unable to take food from the soil until it is dissolved, so the animal 

 is unable to use food for its nourishment until it has been digested. Digestion begins with masti- 

 cation and continues up to the time the undigested part 

 of the food leaves the body. The mineral matter, crude 

 protein, fat, sugar, starch, and fiber, each undergoes diges- 

 tion in the alimentary tract. 



Object. To learn the processes of digestion and where 

 in the alimentary tract each food is digested. 



Materials. Colored pencils and pictures of the diges- 

 tive tracts of animals to be studied. 



•-•'tongue 



lower mandible' 

 0/ beak 



second portion 

 of esophayus \ 



proventriculus, or 

 glandular stomach 



gizzard, or. 

 muscular stomach 



small intestines 

 entrance of 

 urinary duct 



rectum 



•cloaca 



Fig. 138. The digestive tract of a chicken 

 Diagram from Iowa State College 



Directions. 1 . Using different colored pencils or ink to 

 represent mineral matter, crude protein, fat, sugar, starch, 

 and fiber, respectively, trace their passage through the 

 digestive tract to the place where each is largely changed 

 into another product. Indicate in writing the manner in 

 which each change is brought about. Note in what organ 

 of the body each change takes place. Explain where and 

 how the digested food is absorbed into the circulatory 

 system. Determine where and for what purpose each 

 kind of digested food is used by the animal. 



2. Make a careful study of the digestive tracts of the 

 chicken, the horse, and the ox as shown in the diagrams 

 and described in reference books. Also state in writing the 

 important particulars in which each differs from the other. 



Show how fowls masticate their food, and how in detail the ox masticates food, and what is 



meant by the expression, "chewing its cud." To what class of animals is the expression applied? 



Indicate the difference in their systems 



with respect to their ability to handle 



coarse fodders. 



3. Describe the digestive processes rectum 



which go on in the mouth and name 



the compounds which are active in 



bringing about the changes which occur 



there. Describe the changes which take 



place in the simple stomach, and name 



the juices which are active. State 



what changes occur in the small in- 

 testines. Indicate the action of the 



pancreas and the liver. What proc- 

 esses take place in the large intestines ? 



State where and how each part of the 



digested material is assimilated by the 



body. Explain how the fats, carbohydrates, and protein are digested 



roof of mouth 

 tongue ! 

 pharynx- 



— large colon 

 small colon 



Fig. 139. The digestive tract of a horse 

 From Iowa State College 



Mention the part which bacteria 

 play in the digestive process and in which class of animals they are the most important. 



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