SALTS 449 



to acidity alone, but also part to the ion itself. Further evidence 

 lies in the fact that the solutions of the sodium, magnesium, 

 lithium, and calcium ions were all of the same acidity, yet there 

 was a pronounced difference in the effect of these solutions on the 

 stretching capacity of protoplasm. 



Loeb did well in calling attention to an experimental error, 

 but experiment proves and opinion upholds a specific ion 

 effect. It would be difficult to escape this conclusion in the face 

 of the definite need of organisms for certain ions and the marked 

 preference shown by plants and animals for ions that are physi- 

 cally as closely related as are sodium and potassium or calcium 

 and magnesium. 



Organic Salts.— While this chapter is concerned primarily 

 with inorganic salts, brief reference may be made to certain 

 organic salts which may play an important role in protoplasm, 

 viz., the soaps. A soap is a metallic salt of a higher fatty acid, 

 usually an alkali metal united to oleic, stearic, or palmitic acid; 

 thus, sodium stearate is NaCi8H3502. Soaps are minor ingredi- 

 ents of protoplasm, small in quantity but possibly exercising 

 considerable influence. They possess some of the properties of 

 crystalloids, in that they form crystalline structures and ionize; 

 and of colloids, in that they form elastic jellies. One possible 

 role of soaps in protoplasm is the saponification of fats and the 

 maintenance of the protoplasmic emulsion. 



Biological and Medical Problems in Salt Concentrations. — 

 Life is the expression of the interrelationship between protoplasm 

 and its environment. In the composition of this environment, 

 salts play a part second only to that played by water. The salt 

 balance between a living cell and the solution that bathes it 

 must (ordinarily) be accurately maintained, or else illness and 

 death result. There often appear to be striking exceptions to 

 this, but usually they are only apparent exceptions. Thus, 

 Mast finds that Amoeba without food moves normally, divides, 

 and lives several (a maximum of 16) days in water of very high 

 purity. Salts in proper concentration, both single and mixed, 

 prolong the life (a maximum of 18 days in single salts and 22 in 

 mixed ones). The experiment does not reveal the ill effects of 

 the absence of salt while the animal lived. 



Organisms sometimes show a remarkable adjustment to a 

 change in salt environment. The most surprising examples of 



