CHAPTER XIX. 

 ABSORPTION. 



(See also p. 409 et seq., section on Purgatives.) 



THE absorption of food materials or alien substances is accom- 

 plished by a dissolving current which originates in the intestines and 

 flows through the body. There it parts with some substances and 

 takes up others, finally excreting through the various glands, but 

 especially the kidneys, such crystalloids as have become superfluous. 



Substances may be absorbed from other places, through the skin 

 and mucous membranes, from peritoneum and pleura. This may 

 occur when exudates have collected and have been absorbed, or when 

 the substances have been injected. In some animals, as in the frog, 

 absorption of water occurs only through the skin. Subcutaneous, 

 intramuscular and intravenous injections are made in order to intro- 

 duce substance into the body without their passage through the 

 intestines. The absorption of substances thus introduced into the 

 organism is termed parenteral absorption. 



Alimentary Absorption. 



Besides the fluids which are taken with food, there is daily poured 

 into the intestines of adult men 700 to 1000 c.c. of saliva, 600 to 

 900 c.c. of bile, 600 to 800 c.c. of pancreatic juice, 1000 to 2000 c.c. of 

 gastric juice, 200 c.c. of succus entericus; in all 3.1 to 4.9 liters. 

 Inasmuch as in healthy men hardly 400 to 500 c.c. of this fluid are 

 evacuated with the feces, there must normally occur a reabsorption 

 of 2.7 to 4.5 liters. To this must be added 1 to 1.5 liters of liquid food, 

 so that the alimentary tract absorbs about 6 liters daily quite a 

 considerable task. 



With the water, dissolved substances are also absorbed. Inas- 

 much as the intestinal membrane is impassable for colloids (with 

 the exception of very finely emulsified fats), it is the function of 

 the alimentary tract with the help of the ferments to convert the 

 foodstuffs into an easily diffusible condition. 



The intestinal tube is a membrane, which separates the interior 

 of the body from the foods introduced and the digestive juices. It 

 is the function of research to discover what forces drive these solutions 



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