PHYSIOLOGICAL ABSORPTION. 343 



With " strong " solutions, where the water absorption is 

 entirely " physiological," while the salt absorption is partly 

 " physiological " and partly " physical," the net result of in- 

 terfering with the " physiological" action must be to reduce 

 the absorption of water out of proportion to that of salt. 



On the other hand, with " weak " solutions, where the 

 salt absorption is purely "physiological," while the water 

 absorption is partly "physiological " and partly " physical," 

 the effect will be a diminution of salt absorption out of 

 proportion to that of water absorption. 



Heidenhain has found in sodic fluoride, added to '04 to 

 •05 per cent, of the solutions, a means of poisoning the 

 epithelium, and he finds that when added to the "strong" 

 solutions of sodic chloride, undergoing absorption in a loop 

 of dog's gut, the number representing the ratio ol salt 

 absorption to water absorption increases. As we would 

 expect, the absolute salt absorption is found to be also 

 diminished, as well as that of water, but the latter out of all 

 proportion to the former. 



The action is recovered from, but only slowly ; thus in 

 one case using one and the same loop of gut, it was found 

 that after contrasting the absorption without and with the 

 addition of sodic fluoride, a third experiment without the 

 fluoride showed that it took the loop forty minutes to do the 

 absorption work that before had been accomplished in 

 twenty. 



With "weak" solution of sodic chloride the reverse 

 results are obtained ; the salt absorption is diminished out 

 of all proportion to the water absorption, so that the ratio 

 salt absorption to water absorption falls, as it should accord- 

 ing to the theory. In one experiment the water absorption 

 was not halved, while the salt absorption fell to a seventh 

 of that occurring before the use of the fluoride. 



Sodic fluoride, then, is a reagent affecting the water 

 absorption more when "strong" solutions of sodic chloride 

 are undergoing absorption, the salt absorption more when 

 the solutions are " weak," i.e., it affects in each case that 

 part of the total absorption which is to be regarded as of 

 " physiological " rather than " physical " origin. 



