Oil emulsions with casein, gliadin, cholesterin, 

 or cephaelin as the aqueous phase, are of the 

 water-in-oil type and are reversible with NaOH. 



Oil emulsions in which saponin (senegin, 

 smilacin), gelatose, gum arabic, albumin, leci- 

 thin, or a plant extract is the emulsifier, arc 

 oil-in-water systems which are not reversible 

 with BaCb. 



It is of interest to note that of three proteins, 

 all present in protoplasm, the most abundant 

 one, albumin, does not permit reversal, while 

 the two others do; and of two lipoids, both 

 constituents of living matter, one, lecithin, 

 does not, and one, chloresterin, does permit re- 

 versal. Further, the plant extract (obtained by 

 grinding and pressing fresh spinach), which 

 one might expect to approach somewhat the 

 chemical make-up of protoplasm, does not per- 

 mit reversal. 



Who can tell what the emulsifier in the sup- 

 posed living emulsion actually is? 



Since the hypothesis of Clowes rests on the 

 assumption that the emulsifier in protoplasm is 

 of that type which forms an emulsion Avhich is 

 reversible with BaCb or NaOH, and since cer- 

 tain of the substances here experimented with 

 as emulsifiers, are very abundant in protoplasm 

 but form emulsions which are not reversible 

 with BaCb or NaOH, one is forced to conclude 

 that, in view of the fact that we are totally ig- 

 norant of the actual nature of the active emul- 

 sifier in living matter, a theory of the mechan- 

 ism of permeability changes which is based on 

 the behavior of only one group of emulsions, 

 must be regarded as a purely speculative hy- 

 pothesis which rests on very uncertain evidence. 

 It is of further interest to note that NaCl 

 will not reverse any of the reversible emulsions 

 here studied, yet it is this salt which causes (in 

 the opinion of some investigators) such a pro- 

 nounced increase in the permeability of proto- 

 plasm. 



