ABSORPTION. 145 



factive bacteria one of the most important conditions for their life, 

 and inhibits their activity. Three to five quarts of water daily can 

 be absorbed; but the faeces become thin or paplike. The jejunum 

 absorbs better than the ileum. The dilute solutions of salts are 

 more easily absorbed than the concentrated solutions. When col- 

 ored solutions were placed in the intestines, it was found that they 

 passed through the epithelial cells and through the intercellular 

 spaces. 



The absorption of water and salts from the intestines does not 

 follow the laws of osmosis. If you destroy the epithelium with 

 sodium fluoride, then absorption takes place only according to the 

 laws of osmosis. When the epithelium is injured, there is a 

 diffusion-stream from the blood, through the intestinal wall, into the 

 intestinal cavity; it seems to be through the intestinal epithelium. 

 Intestinal absorption depends upon imbibition, intestinal pressure, 

 and diffusion. The intestinal pressure is increased by the respira- 

 tory movements, by peristalsis, and by the weight of the intestines. 



The water and its salts in solution go into the blood-vessels of 

 the villi because they are immediately beneath the basement mem- 

 brane of the villus, whilst the chyle-vessel is separated from, the 

 capillaries by the stroma of the villus. The duodenum is the prin- 

 cipal seat of absorption of the iron salts, the spleen their storage- 

 house, and the colon their place of excretion. 



Carbohydrates. 



The carbohydrates are absorbed in the intestine up to 500 

 grams per day. The monosaccharides, dextrose, laevulose, and gal- 

 actose, are absorbed as such; whilst the disaccharides, cane-sugar 

 and milk-sugar, are first inverted into dextrose, laevulose, and gal- 

 actose, the latter formed by the action of inverting ferments on 

 lactose. The chief quantity of -the carbohydrates in the food is the 

 polysaccharides, and of these starch is a prominent one. Starch is 

 not soluble in either hot or cold water. Its cellulose coat must be 

 removed by cooking and baking, and still it is not fitted for absorp- 

 tion; it must be acted upon by the diastasic ferments of the saliva 

 and pancreatic juice, being hydrolyzed by them, forming first soluble 

 starch, then dextrin, isomaltose, maltose, and a little glucose. The 

 starch remains but a short time in the mouth, and in the stomach 

 the ptyalin acts but a short time, because the free HC1 stops its 

 activity; hence the amylopsin is the chief agent .in the change of 

 starch into maltose. Here the isomaltose is changed into maltose, 



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