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COLLOIDS IN BIOLOGY AND MEDICINE 



of crystalloids through the intestinal membrane. For many years 

 it was believed that osmotic forces were involved. This conception 

 proved to be a serious obstacle to further progress since it diverted 

 attention in a direction offering no prospect of results. It was only 

 when swelling and shrinking were recognized as the dominant factors 

 in absorption that it became possible to understand many experi- 

 mental data which previously had been inexplicable. 



The recognition of the importance of swelling for absorption dates 

 from F. HOFMEISTER. He said, " The essentially absorbing appara- 

 tus, the intestinal epithelium, is possessed of the power to swell. " 1 



Water and Crystalloids. 



If water or dilute salt solution is introduced into a loop of in- 

 testines, it is absorbed more or less rapidly. If the intestine be- 

 haved like a parchment membrane and the absorption of the fluids 

 was brought about by the osmotic pressure of the body juices, water 

 would be most rapidly absorbed. This is, however, not the case. 

 According to G. O. GUMILEVSKIJ,* pure water is less rapidly absorbed 

 than 0.25 per cent NaCl solution. Accordingly, the intestine behaves 

 like gelatin which swells more in salt solution than in pure water. 



The matter becomes more complicated if we consider quantita- 

 tively the absorption of water and salt in hypo tonic and hypertonic salt 

 solutions. We shall study the experimental figures of M. HEIDEN- 

 HAIN, who placed sodium chorid solutions of various concentrations 

 in loops of small intestine of a dog and permitted them to remain 

 there for 15 minutes. 



A glance suffices to show that this experiment cannot be explained 

 by the osmotic relations: with a parchment tube having slight swell- 

 ing capacity surrounded by physiological salt solution, the amount 

 of water recovered would have to be more than 117 and 120 c.c. 



1 I would venture the suggestion that many poisons which are supposed to 

 lose their "physiological components" by absorption through the intestines, such 

 as NaFl, osmic acid, etc., markedly modify the swelling capacity. 



