138 WILLIAM SEIFRIZ 



mechanism of permeability changes in the protoplasmic membrane. 

 Before we attempt to visualize so complex a vital phenomenon on the 

 basis of so simple a mechanical process as phase reversal in emulsions, 

 it is only the part of wisdom to thoroughly investigate the assumptions 

 on which our analogy rests. 



SUMMARY 



1. Olive oil emulsions in which one of the soaps, sodium oleate or 

 sodium stearate, is the emulsifie'r, are oil-in-water systems which are 

 reversible with BaCl2. 



2. Oil emulsions with casein, gliadin, cholesterin, or cephalin as the 

 aqueous phase, form water-in-oil systems which are reversible with 

 NaOH. 



3. Oil emulsions in which saponin (senegin, smilacin), gelatose, gum 

 arabic, albumin, lecithin, or plant extract, is the emulsifier, form oil-in- 

 water systems which are not reversible with BaCl2. 



4. Since the hypothesis of Clowes, on the mechanism of permeability 

 changes in the plasma membrane, rests on the assumption that the 

 emulsifier in protoplasm is of that type which form an emulsion that is 

 reversible with BaCl 2 or NaOH and since certain of the substances here 

 experimented with as emulsifiers, are very abundant in protoplasm but 

 form emulsions which are not reversible with BaCl 2 or NaOH, one 

 is forced to conclude that, since we are totally ignorant of the actual 

 nature of the emulsifier in protoplasm, a theory of the mechanism of 

 permeability changes which is based on the behavior of only one type of 

 emulsion in the presence of certain ions, must be regarded as a purely 

 speculative hypothesis which rests on very uncertain evidence. 



5. CaCl 2 and Ba(OH) 2 are both like BaCl 2 in their influence on the 

 emulsions investigated, with one exception. 



6. NaCl will not reverse any of the emulsions here investigated. 

 The effect of NaCl on the emulsions is to cause "breaking," that is, to 

 cause a separation of the two liquid phases. There is little evidence to 

 support the belief that NaCl tends to promote the formation of oil-in- 

 water emulsions. 



7. In view of the striking difference in the reaction of emulsions to 

 NaCl and to NaOH, there seems to be little reason to believe that the 

 behavior of oil emulsions when treated with NaOH serves as a satisfac- 

 tory basis of an explanation of the mechanism of permeability changes 

 occasioned in the plasma membrane by NaCl. 



8. Since both the chloride and the hydroxide of barium and the chlo- 

 ride of calcium will reverse certain oil-in-water emulsions, and since the 

 chloride of sodium will not reverse certain water-in-oil emulsions which 



