126 WILLIAM SEIFRIZ 



An emulsion of oil dispersed in water is a S3 r stem which is readily 

 permeable to water-soluble substances, and an emulsion of water dis- 

 persed in oil is a system which is poorly or not at all permeable to water- 

 soluble substances. Since Na (in the form of the hydroxide and in the 

 emulsions with which Clowes worked) produces an emulsion of the 

 former type, and (in the opinion of Osterhout) increases protoplasmic 

 permeability, and since Ca produces an emulsion of the latter type and 

 decreases the permeability of protoplasm, Clowes conceives of the 

 living membrane as a fine emulsion which is in a state of equilibrium at 

 or near the reversal point. In the presence of Na the emulsion at the 

 surface of protoplasm would tend more toward the oil-in-water type, 

 and in the presence of Ca it would approach the water-in-oil condition, 

 never being fully of the one or the other type while the cell is living. 

 Clowes looks upon living protoplasm in contact 'with water as a system 

 which is, within the protoplasmic mass, a dispersion of proteins, lipoids, 

 etc., in water and, at its surface, a system of the reverse type of struc- 

 ture in which water is dispersed in a continuous fatty or lipoid phase. 

 The dispersion at the surface is not, however, complete, but rather a 

 system in which the fatty continuous phase is permeated by water 

 channels, i.e., it is at the reversal point. This sponge or honey-comb 

 structure of the surface layer of protoplasm Clowes considers as capable 

 of being modified by calcium salts, anesthetics, etc., in such a way that 

 a system is formed in which the water communications are decreased or 

 completely cut off. Salts of monovalent cations, on the other hand, 

 would tend to produce a system in which the water channels are more 

 extensive. 



Clowes' hypothesis is based on three assumptions: first, that proto- 

 plasm is, in its colloidal nature, an emulsion; second, that this emulsion 

 is capable of phase reversal; and third, that the emulsifler active in 

 protoplasm is either soap or a substance which behaves as does soap 

 when in the presence of certain mono- and bivalent cations. Without 

 intending to assert that the first assumption is untrue, it is nevertheless 

 well to point out that we are totally ignorant of the actual physical 

 nature of the ultramicroscopic particles of the living colloid. This being 

 the case, any convenient hypothesis can be postulated. One cannot, 

 therefore, deny the possibility of protoplasm being a colloidal emulsion, 

 that is, a system in which liquid, ultramicroscopic particles, in a high 

 state of dispersion, are suspended in a liquid medium. The actual 

 physical nature of the colloidal particles of the living system we cannot 

 yet hope to determine,but after all, as Hatschek (8) points out, the dis- 

 tinction between liquid and solid becomes rather vague with particles 

 approaching ultramicroscopic dimensions. 



