FROM THE SMALL INTESTINE 655 



did not rise during absorption. This result could be explained 

 as due to the water absorption being so delayed by the osmotic 

 pressure of the NaCl that the uptake of dextrose could still 

 keep pace with it. Now, from these data it would be expected 

 that if the absorptions of 2 per cent, solutions of dextrose in 

 water and in 6 per cent. NaCl solution were compared, a greater 

 quantity of dextrose would be absorbed from the former solution 

 than from the latter ; because the concentration of dextrose in 

 the former solution will rise during absorption up to 4 per cent., 

 but will remain unaltered in the other. This expectation, however, 

 was not fulfilled. Reid found in most of his experiments that 

 just as much dextrose was absorbed from the salted as from 

 the unsalted solution, i.e. from the low as from the high con- 

 centration of dextrose. And in two animals which were in full 

 digestion with white lacteals he found that much more dextrose 

 was absorbed from the salted solution. He associated this 

 unexpected result with the presence of NaCl in one of the 

 solutions, and in support of this idea he found that more 

 dextrose was absorbed from a solution salted with KC1 than 

 from one salted with NaCl. He sees in these results a clear 

 indication of ionic action ; and every one will agree with him. 

 But when he goes on to explain the ionic action as due to its 

 producing a stimulation of a specific cell activity, he may be 

 right, but he is going far beyond what is justified by our know- 

 ledge of ionic action in general. In fact, these experiments are but 

 another instance of the impossibility of interpreting at present the 

 results of experiments on intestinal absorption where solutions of 

 electrolytes are allowed to influence the absorbing cell membrane. 

 Conclusion. We have reviewed the more important experi- 

 ments dealing with the mechanism of absorption from the small 

 intestine with the object of finding out how much is left 

 unexplained by known physical processes, and therefore how much 

 must be attributed to vital action. We have seen that, whilst 

 there is no one experimental result which can be pointed to as 

 indicating with absolute certainty vital action, there are many 

 which cannot be satisfactorily explained by our present know- 

 ledge of physical processes in relation to living cells. Nevertheless 

 we have seen that physical processes can explain much ; and in 

 forming a working hypothesis on intestinal absorption we are 

 driven at present to leave vital activity largely out of account 



