DIGESTION AND ABSORPTION 363 



as we have seen, sugar is taken from the blood and stored as 

 glycogen. From the liver, the food within the blood is sent to 

 the heart, from there is pumped to the lungs, from there returns 

 to the heart, and is pumped to the tissues of the body. A large 

 amount of water and some salts are also absorbed through the 

 walls of the stomach and intestine as the food passes on its course. 

 The fats in the form of soaps and fatty acids pass into the space 

 in the center of the villus. Later they are changed into fats again, 

 probably in certain groups of gland cells known as mesenteric 

 glands, and eventually reach the blood by way of the thoracic 

 duct without passing through the liver. 



Large Intestine. The large intestine has somewhat the same struc- 

 ture as the small intestine, except that the diameter is much greater. It 

 also contains no villi. Considerable absorption, however, takes place 

 through its walls as the mass of food and refuse material is slowly pushed 

 along by the muscles within its walls. 



In this portion of the intestine live millions of bacteria, some of which 

 manufacture poisonous substances from the foods on which they live. 

 These substances are easily absorbed through the walls of the large in- 

 testine, and passing into the blood, cause headaches or sometimes serious 

 trouble. Hence it follows that the lower bowel should be emptied of this 

 matter as frequently as possible, at least once a day. Constipation is 

 one of the most serious evils the American people have to deal with, and 

 it is largely brought about by the artificial life which we lead, with its 

 lack of exercise, fresh air, and sleep. 



Vermiform Appendix. At the point where the small intestine widens 

 to form the large intestine, a baglike pouch is formed. From one side of 

 this pouch is given off a small tube about four inches long, closed at the 

 lower end. This tube, the function of which in man is unknown, is 

 called the vermiform appendix. It has come to have unpleasant noto- 

 riety in late years, as the site of serious inflammation. It often becomes 

 necessary to remove the appendix in order to prevent this inflammation 

 from spreading to the surrounding tissues. 



Hygienic Habits of Eating ; the Causes and Prevention of Dys- 

 pepsia. From the contents of the foregoing chapter it is evident 

 that the object of the process of digestion is to break up solid food 

 so that it may be absorbed to form part of the blood. Any habits 

 we may form of thoroughly chewing our food will evidently aid 

 in this process. Undoubtedly much of the distress known as 

 dyspepsia is due to too hasty meals with consequent lack of proper 



