OF VITAL PHENOMENA 1 1 1 



(1908) observed that a solution of tartaric acid passes through 

 pig's bladder into pure water (negative osmose). Evidently the 

 acid reversed the charge on the membrane, making it positive, 

 the greater speed of the positive ion causing the negative osmose. 

 Although Flusin adopts another explanation for anomalous os- 

 mose, Girard (1908-13) shows conclusively that electroendos- 

 mose is at least in part the correct explanation. If the solutions 

 on the two sides of the membrane are isotonic the driving force 

 of osmose is the diffusion potential causing electroendosmose. 

 In the following table the first column gives the solutes used in 

 the isotonic solutions, the second the charge of the membrane, 

 the third column the direction of the emf (positive current), 

 the fourth the direction, and the fifth the relative magnitude of 

 the osmose. 



Isotonic membrane diffusion direction of magnitude of 



solutions potential emf osmose osmose 



Sucrose iff 



Tartaric ac. + ' ' 33 



Sucrose . . 



Pb(NO a ) 2 + l l I0 



Sucrose . . 



K 2 C0 3 - T l 3 ° 



Oxalic ac. 



NapSO^ 



+ 44 20 



With a membrane separating isotonic solutions of NaCl and 

 KC1 there was no emf and no osmose. The same was true of 

 KC1 and Na 2 S0 4 . Although these experiments of Girard ante- 

 date those of Bartell and Hocker, the latter have been described 

 first on account of the simple character of the membranes and 

 the remarkable relation of the diameter of the pores to their 

 properties. Although it may not have been shown that all 

 anomalies in osmose are due to electroendosmose, it seems un- 

 necessary at present to accept the hypothesis of Flusin that 

 osmose takes place through the membrane from the side of least 

 swelling (smaller pores) to the side of greatest swelling (largest 

 pores). At any rate, the size of the pores in porcelain mem- 

 branes is not affected by the character of the solute (Hofmeister 

 series). 



