VALUE OF MINERAL SALTS. 15 



matter combined with the plasma proteids. "All proteins" occurring 

 in the living- organisms are combined with mineral substances, whereby 

 the proteins concerned acquire specific properties and functional 

 signification in the organisms/' 



Since in a normally developed plant each nutrient must be present 

 in definite amount, it is evident that normal growth can not be expected 

 when any one of the mineral nutrients is present in insufficient quantity, 

 no matter what amount of the other mineral nutrients may be avail- 

 able. The production of the organic matter of a plant of definite 

 size depends therefore upon that mineral nutrient which is present 

 .in relatively smallest amount. For example, it is clear that the divi- 

 sion and multiplication of cells depends upon the development of the 

 nucleus, and that upon the continuous formation of nucleoproteids. 

 Hence when phosphoric acid is present in but small amount, only a 

 corresponding amount of nucleoproteid can be produced. This holds 

 good likewise for lime, since we infer that the lime compounds of 

 nucleoproteids are concerned in the building up of the nucleus. Potas- 

 sium is essential to organic synthesis. Accordingly when but little 

 potassium is available, the organic matter in the plant will depend on 

 this amount, no matter what amount of the other mineral nutrients 

 be at hand. This fact, which means that the size of the harvest 

 depends upon the mineral nutrients present in least amount, is known 

 &sZ,iebig's Lam of the Minimum. Liebig inferred this law from gen- 

 eral principles and without any knowledge of the special function of 

 each mineral nutrient. 



It may be proper here to call attention to another phenomenon, first 

 recognized b} T Wolff. He determined the minimum of each mineral 

 nutrient necessary for the normal development of the oat plant when 

 the other mineral nutrients were in excess, and found that when all 

 the mineral nutrients are offered in the determined minimum amounts 

 at the same time it is impossible for the plants to flower and fruit 

 normally. When only the absolutely necessary minimum of one of 

 the nutrients is offered a certain surplus of some of the others must 

 be present. 



THE LOW ATOMIC WEIGHT OF THE MINERAL NUTRIENTS. 



A review of the elements necessary for organic life shows at once 

 that they have low atomic weights, iron, with an atomic weig'ht of 56, 

 having the highest among them. This is due, according to Leo Errera, 

 not only to their more frequent occurrence in the various compounds 

 making up the earth's crust, but also to their higher specific heat. 



"While "protein" is the general denomination of all kinds of albuminous sub- 

 stances, the word "proteid" applies especially to the complex proteins, e. g., 

 nucleoalbumin, mucin, haemoglobin, etc, 



