HOW MOLECULES MAKE MASSES 57 



double and plural colloidal protection. The doubly protected solu- 

 tions gave a stable calcium phosphate sol, precipitable with acid and 

 with rennin (1908). 34 



Although U. S. Patent No. 1,259,708 was obtained to cover multiple 

 colloidal protection, it was later found that double protection had 

 been used empirically — in fact, it is referred to in the foregoing quo- 

 tation from Ord's book. The so-called "grainless" photographic emul- 

 sion of G. Lippmann (Nobel prize, 1908) is made by dividing the 

 protective gelatin equally between the silver nitrate and the halide 

 solutions. M. Carey Lea produced some of his silver "photohaloids" 

 in a similar manner, and Lobry de Bruyn 35 also used gelatin in both 

 reacting solutions. 



Plural protection is illustrated in the gluten of wheat flour, which 

 contains a protective colloidal system consisting mainly of the fol- 

 lowing: 



Gliadin, which forms an opalescent colloidal solution in water, 



precipitated by sodium chloride; 

 Glutenin, which is insoluble in water or saline solutions, but dis- 

 solves in weak acid or alkali, and reprecipitates on neutral- 

 ization; 

 Globulin and albumin, which are soluble in sodium chloride 

 solutions. 

 Salt, used from time immemorial in making bread, and the feeble 

 acidity developed by the yeast help to produce desirable bread-making 

 properties in the protective colloids present by means of what may be 

 called a cumulative protective system or mixture. Hard water (sul- 

 fates) hardens the gluten, while alkaline water disintegrates it and 

 destroys its elasticity. Even distilled water yields a sticky dough. 



The multiform effects arising from the interplay of crystalliza- 

 tion forces and specific colloids lead one to suspect that the size, 

 shape, and nature of many biological structures are thus domi- 

 nated. 36 Plant and animal cells and circulating fluids abound in 

 substances which are capable of acting as protectors. As a result, 

 any precipitate forming by reactions between fluids, or even by 

 catalysis at specific surfaces, would tend to be highly colloidal be- 

 cause of double or multiple colloidal protection, and to remain so 

 unless the adsorbed layers function as cohesive colloids, in which 

 case particulate units (e.g., starch grains, cellulose units and fibers) 

 or tissue structures (e.g., wood, fibrous tissue) may emerge. 

 Naturally, the formation of such structures may also involve other 

 factors — enzymes, for example. J. Wolf and A. Fernbach 37 ex- 

 tracted from green cereals an enzyme, coagulase, capable of pre- 

 cipitating starch from its solutions. 



