86 THE THEORY OF IONS 



with marvellous rapidity. Changes of shape and 

 the internal structure of protoplasm also have 

 analogies in the variations visible in dead colloids. 

 But that all living substance is liquid meets with 

 greater difficulties than the assumption of a solid 

 state. Thus, for instance, an inner stabile differen- 

 tiation in a liquid is impossible, whereas the proteins 

 are stabile. While every part of an amoeba is 

 equally capable of the functions of assimilation, 

 stimulation and movement, every element in the 

 mass may become a surface element, or conversely. 

 Nevertheless " there exist peculiarities in unicellular 

 organisms, and in the individual cells of higher 

 animals, which can scarcely be interpreted otherwise 

 than as expressions of polarity.* Under this heading 

 belong " the fact that absorption and secretion take 

 place predominantly in certain directions, the de- 

 pendence of muscular stimulation upon the angle of 

 the current and the direction of the muscular fibril, 

 and the polarity of the phenomena of degeneration 

 in plants and animals. These phenomena indicate 

 a persistent inner differentiation which can scarcely 

 be explained without the assumption of a solid 

 orientation of the particles of living matter, "f 

 Pauli considers that many of the phenomena of 

 living tissues are to be understood through a study 

 of the non-living colloids. The gels or solid colloids 

 such as agar-agar and gelatine show some of the 

 characteristics of living tissues. Such a jelly does 

 not take up any other colloid brought into contact 



* Pauli's " Physical Chemistry in the Service of Medicine," 

 p. 29. 



t Loc. cit. 



