180 PHYSIOLOGY. 



Summary. I . The chief work in digestion is to render the food 

 liquid, soluble, and in condition to be absorbed and become part of the 

 blood. 



2. The digestive system consists of a long tube, through which 

 the food passes, being subjected to mechanical and chemical processes 

 to liquefy and otherwise make the food ready to become blood. 



3. The teeth grind the food. 



4. The food is soaked and acted on by the saliva, gastric juice, 

 intestinal juice, bile, and pancreatic juice. 



5. These liquids are formed from the blood by glands. A gland 

 is a structure, usually tubular or saclike, surrounded by capillaries, 

 which give off lymph around the gland. The gland cells take part 

 of the lymph and form the "secretion," which is usually poured out 

 on a surface by means of a narrow tube, or duct. 



6. The salivary glands, pancreas, and liver are compound glands. 

 The gastric and intestinal glands are simple. 



7. The first part of swallowing is voluntary. Through the gullet 

 the food is pushed by the shortening of the circular muscle fibers. 



8. The liver receives blood from the hepatic artery and from 

 the portal vein, but is drained by one vein, the hepatic, which empties 

 into the postcaval vein. 



9. Saliva acts only on starch, gastric juice on proteids, bile on 

 fats ; pancreatic juice acts on all three of these foodstuffs. 



Questions. i. Why does the physician examine the tongue of his 

 patient? 



2. What is the "mumps"? 



3. Why is one more likely to choke if he thinks about the process 

 of swallowing? 



4. What are the peculiarities of a cow's stomach? 



5 . What is the meaning of biliousness ? 



6. Why is there a difference in the length of the intestine in a cat 

 and a sheep? 



7. What is colic? 



