Growth and Colloidal Reactions. 3 



mixture of the two substances in which the two would exist separately 

 in their characteristic emulsion. The amino-acids, on the other hand, 

 diffuse readily into the colloids, and these may be visualized as being 

 aggregated with the carbohydrate colloid, in both phases, and, as may 

 be seen by reference to Chapter II, they set up water-relations differ- 

 ent in some features from those determined by the hydrogen and 

 hydroxyl ions. 



The place of the lipins in the hydration mechanism can not at present 

 be made the subject of profitable conjecture. While lecithin, for 

 example, is known to adsorb water, its part in the living matter of the 

 plant must be all but negligible, as it by no means bulks as large here 

 as in the animal. 



The general effect of the salts is to lessen the imbibition capacity of 

 agar-protein mixtures when in simple solutions from a concentration 

 of 2 N to 0.00005 N. Set in action with acids or in antagonistic rela- 

 tions, other effects are produced in sections of living plants. Although 

 one of the subjects receiving the most attention in colloidal physics, 

 and although extensive experiments with tissues and cell-masses of 

 plants and animals dealing with the matter have been made, it is not 

 yet definitely determined whether or not the action of a salt upon a 

 biocoUoid may be expressed by the algebraic summation of its acid and 

 base as originally proposed by Pauli for gelatine, or whether the effect 

 is due partly to other factors. 



The extent to which protoplasm may be made up of dense particles 

 of substances of a single category, such as protein or globuhn granules, 

 starch grains, or of minute masses of more highly hydrated strands or 

 globules of albimiin or of carbohydrates, or lipins, or of combinations 

 such as those of Upin and protein in the mitochondria, can not be 

 visiialized. Neither is it possible to say whether the carbohydrate 

 and protein molecules are equally aggregated in both the continuous or 

 external phase and the discontinuous or internal phase of the gel, or 

 whether one predominates in each phase according to the proportions 

 in which they are combined. In any case phase reversals are possible. 

 The imbibitional reactions of the living matter of plants are seen, how- 

 ever, to be parallel to those of a salted carbohydrate-protein gel com- 

 bined in a high state of dispersion and questions as to systemic arrange- 

 ment must be left in abeyance for the present. So far as known, it is 

 the actual composition and relative proportions of the substances of 

 the main organic groups and the amount, the stage, and sequence of 

 incorporation of the infiltrated salts that constitute variables of the first 

 order of importance in the determination of the behavior of the mass. 



The chief distinction between the protoplasm of plants and that of 

 animals may be taken to lie within the play of these major features. 

 Living matter in animals includes lipins and consists predominantly of 

 nitrogenous material, which displays maximum hydration capacity in 



