PHYSIOLOGICAL ABSORPTION. 341 



passed faster than the salt, i.e., the ratio salt absorption to 

 water absorption is less than unity. 



This being so, we gather that a " normal " solution of 

 sodic chloride is absorbed unchanged in percentage by a 

 "physiological" action, but that with "weak" or "strong" 

 solutions, the "physical" osmotic action must be super- 

 added. 



"In der that weisen schon manche der bisherigen 

 Erfahrungen darauf hin, dass die Vorgange bei der Resorp- 

 tion sich nicht einfach auf die eine oder die andere Weise 

 deuten lassen, dass vielmehr physiologische und physika- 

 lische Factoren in einander greifen, mit je nach den 

 Bedingungen wechselnder Energie, um die Resorption von 

 Salzlosungen herzustellen " (Heidenhain). 



Heidenhain, therefore, proceeds to study more minutely 

 the absorption of sodic chloride solutions above and below 

 " normal " strength, upon the assumption that in all cases 

 a "physiological" absorption at " normal " strength occurs, 

 but that the net result is affected in one direction or the 

 other by the concomitant osmotic conditions. 



With a solution of sodic chloride in the gut, of higher 

 percentage than the blood (1 to 1*5 per cent, solutions were 

 used), " physically " sodic chloride must pass to the blood, 

 and water must pass into the gut as the total osmotic pres- 

 sure of the solution in the gut exceeds that of the serum. 

 Since, however, the actual experiments show that the water is 

 absorbed from the gut under the circumstances, the " physio- 

 logical " output of water exceeds the "physical" income. 

 The absorption, then, of this " strong " solution of salt may 

 be divided into a " physiological " moiety in which salt and 

 water are passing out of the gut, and a " physical" moiety 

 in which salt alone is concerned, for the "physical " water 

 stream is swamped by the opposing stream of "physio- 

 logical " origin. 



Thus the salt absorption here is partly " physical ,: and 

 partly "physiological," while the water absorption is en- 

 tirely " physiological ". 



If the percentage of salt in the " strong " solution be 

 raised to about 2 per cent., the increase in osmotic pressure 



