SOAPS, PROTEIN DERIVATIVES AND TISSUES 229 



reasonable to consider this proof that the system water-dis- 

 solved-in-sodium-caseinate is something different from a solution 

 of scKlium-caseinate-in-water. It must be admitted either (1) that 

 indicator methods may not be applied to such a system or that if 

 they are applicable (2) it contains no ions. We reemphasize the 

 point because to our minds the tissues of the body, including the 

 blood and lymph, are such solutions of water % ^^^^^^^^ 

 in protein (protoplasm) and that, like a con- 

 centrated sodium caseinate/water system, they 

 are electrically neutral, that indicator methods 

 cannot be applied to them without the greatest 

 reserve and that it is fundamentally false to 

 regard them as systems for which the laws of 

 the ordinary dilute solutions may be expected 

 to be valid. 



Slight dilution of the concentrated sodium 

 caseinate/water system with water suffices to turn 

 it pink even when the system is still entirely solid. 

 What turns pink is that portion of the emulsion 

 thus formed which represents the phase, dilute 

 solution of sodium caseinate in water subdivided 

 in the unchanged (more solid) solution of water 

 in sodium caseinate. 



Still further dilution increases the amount of 

 t IK- dilute solution phase and therefore the inten- 

 sity of the pink color (see Fig. 110). When 

 sufficient water is added the system becomes 

 more liquid since it is now composed of a subdi- 

 vision of hydrated sodium caseinate particles 

 within a " true " solution of sodium caseinate as 

 an external, enveloping phase. FIGURE 110. 



On extreme dilution the system becomes in- 

 tensely red (see the upper sections of the tube in Fig. 110) 

 because this is merely a dilute solution of sodium caseinate in 

 water which has at the same time suffered great hydrolysis. 



Just as the solubility and hydration properties of any fatty 

 acid with different bases change as we pass from the alkali metals 

 through the rilk.tliiie earths to the heavy metals, so also do the 

 solubility and hydnition r:ij:ieit ies of casein, and in the same 

 general fashion. The changes observed in the system as one 



