632 THE MECHANISM OF ABSORPTION 



to be considered vital properties of bioplasm, such as synthesis, 

 oxidation, and reduction, are due to the presence of unorganised 

 intracellular ferments. 



We thus arrive at the general conclusion that a solution 

 of an electrolyte may alter the properties of cells, (a) by osmosis, 

 (6) by ionic action, which is certainly electrical and may be also 

 chemical ; whereby the solution alters the permeability, the state 

 of colloidal aggregation, and the other uncertain physical and 

 chemical conditions, &c., upon which the normal physiological 

 activity of bioplasm depends ; (c) by alterations in the activities 

 of unorganised ferments. 



When discussing such a subject as whether absorption is due 

 to physical forces or to the vital activity of cells, it is impossible 

 to ignore the questions, what do we understand by vital action ? 

 and at what point do we consider it necessary to say that a 

 phenomenon is due to it ? Vital activity cannot be held to mean 

 any and all the properties exhibited by living cells, for the 

 same cells when dead may still exhibit some of these properties, 

 which must then be held to have a physical or chemical basis, 

 We shall consider as vital such properties of a cell as are changed 

 in kind and not merely in degree when the same cell is dead. 

 This definition leaves open the question how far vital activity, 

 as denned, may still have a physical and chemical basis. It is 

 simple to interpret a comparison between the properties of the 

 same cell when living and when dead ; but the case is altogether 

 different when we allow solutions of electrolytes and poisons to 

 act upon living cells. Our ignorance of the nature of the changes 

 produced in bioplasm by ions and poisons renders it impossible 

 to interpret the results in terms of vital activity. And to a less 

 extent the same must be true of any other solution which is 

 foreign to the cells in question. 



We must now turn to the more important experiments which 

 deal with absorption by the small intestine. 



Hamburger's Experiments- The older observers had suggested 

 that filtration, diffusion, osmosis, and imbibition might explain 

 intestinal absorption. But Hamburger is the chief modern 

 observer who has attempted to explain by physical processes 

 all the phenomena of intestinal absorption. He has suggested 

 that physical factors other than those enumerated above may 

 play a part, namely, the osmotic pressure of proteids, aspiration 



