80 LIBBIE H. HYMAN 



walls of polygonal cells in which the fluid phase is contained. 

 (Biitschli, '94, p. 216; van Bemmelen, '98; Hardy, '99, '00; 

 Freundlich, '09, p. 474; Bancroft, '13, '14; Clowes, '16a, '16b.) 12 

 If a gel has the reticular structure, neither phase can be said to be 

 external since both are perfectly continuous; but in the alveolar 

 structure the solid phase is external and continuous while the 

 fluid phase is now internal and discontinuous, an exact reversal 

 of the sol condition. The work of Bancroft and Clowes, just 

 cited, in regard to such reversals is of great interest, especially 

 as showing that no change of concentration of any of the gel- 

 forming constituents, nor change of external conditions is neces- 

 sary but only slight alterations of the chemical content. Clowes 

 has very reasonably concluded that the interior of protoplasm 

 is in the sol state with the colloidal proteins, etc., forming the 

 disperse phase, while the surface layer of protoplasm is in the 

 gel state with the fluid part dispersed, and the colloidal con- 

 stituents forming solid walls and constituting the external 

 phase. 



These researches indicate that protoplasm when it passes into 

 the gel state assumes the alveolar or spumoid structure, although 

 of course we are not certain of this. If now, as Biitschli and 

 Rhumbler state, protoplasm is alveolar or spumoid, or whenever 

 or wherever it becomes so structured, one may reasonably con- 

 clude that it has passed into the gel condition, or at least that it 

 has gained properties which are characteristic of solids and not of 

 fluids. This is already evidenced by the behavior of foams, 

 which consist of fluid walls inclosing gases but which exhibit 

 properties not found in either gases or fluids but characteristic of 

 solids. Solid properties must develop to a much greater extent in 

 fluid-fluid or fluid-solid systems when they have an alveolar 

 structure, in proportion to the viscosity of the external phase, 

 which forms the walls of the alveoli. Thus in a viscous material 



12 Objections to this view are of course not wanting, e.g., Howell ('16). I am 

 here merely presenting the view which is favored by the majority of investigators, 

 and attempting to show that if emulsoid colloids have an alveolar structure in 

 the gel state then the existence of alveolar structure in protoplasm (if it occurs) is 

 indicative that such protoplasm is in the gel state. 



