236 SOAPS AND PROTEINS 



It is worthy of note, first, that sodium and chlorid are among 

 the least poisonous of the listed constituents that may be intro- 

 duced into cell protoplasm. It is for this reason that sodium 

 chlorid is the main component of all " physiological " salt solu- 

 tions. 1 Not only do sodium and chlorid appear in protoplasm 

 in largest amounts (in the list of the so-called inorganic " salts ") 

 but they yield, with protein, colloid systems which in physical 

 behavior most closely approximate the physical characteristics 

 of living matter. As we ascend or descend the list of the tabulated 

 bases or acids from sodium or chlorid we encounter protein deriv- 

 atives which are either more hydratable and soluble in water than 

 normal protoplasm or which are less hydratable and soluble. It is 

 t hi* fact, we think, which is associated with the physWbogical, path<>-\ 

 logical and pharmacological action of these elements when introduced * 

 in more than normal concentration into the living mass. When, 

 for example, potassium is introduced in more than normal amount 

 it exerts a " poisonous " action which colloid-chemically evi- 

 dences itself through an increased swelling and an increased 

 fluidity of the affected protoplasm. Ammonium acts similarly, 

 which explains why potassium and ammonium salts, for example, 

 are used therapeutically to render more liquid the mucinous 

 secretions of " catarrhally " affected mucous membranes. 



1 In connection with the analysis of physiological and pathological prob- 

 lems in the terms of colloid-chemistry, definition must be attempted of the 

 nature of such "physiological" salt solutions. Pure water is poisonous 

 because in contact with it, protoplasm hydrolyzes. Free protein in conse- 

 quence precipitates within the cell while " salts" diffuse into the distilled 

 water. Presence of any salt in the pure water reduces such hydrolysis. The 

 salt must, however, be of such nature and of such concentration as not to 

 diffuse into the protoplasm and displace the normal equilibrium existing 

 there between the various basic and acidic elements. Hence the superior 

 value of an NaCl solution over that of any other one salt. But NaCl alone 

 still permits of displacements and loss to the salt solution of constituents like 

 K, Ca, H 2 CO 3 , etc. For this reason a RINGER solution (which contains small 

 amounts of each of these in addition to NaCl) is superior to simple salt solu- 

 tion. Solutions of the sugars (even when present in the same "osmotic" 

 concentration) do not prevent such hydrolysis and hence are little better 

 than distilled water. When properly prepared, a physiological salt solution 

 will have a composition which, as a solution of salts in water, is in equilibrium 

 with the system, solution of water in protoplasm. The protoplasm will 

 now neither take up nor give off water, in other words the two systems 

 will be "isotonic." The concentration of the individual salts in the water 

 will, however, probably not be (and need not be) that of the concentration of 

 these same elements in the hydrated protoplasmic mass. Whence the com- 

 mon finding that "isotonic" solutions are rarely (if ever!) isosmotic. 



