BIOLOGICAL SIGNIFICANCE OF ADSORPTION 1 63 



than the base from dissolved salts. Cellulose is widely distributed 

 in vegetable cell walls, where it is associated to pectic acid. Most 

 cell walls therefore may adsorb basic colors by their pectic mem- 

 brane, and acid dyes by their cellulos constituents. ^ 



Adsorption of acid dyes', such as Congo red, Eosine, Fuchsin . . . 

 is conspicuous in the cell-walls of Sulfuro-bacteriacea, Thiothrix. . . . 

 It is even so strong, that a small quantity of Thiothrix placed in 

 a solution entirely loses color. 



Acidophilous basic gels being widely distributed in the habitat 

 and in histological tissues, may exert an adsorbent effect on the 

 acid ions in the cell, which effect demands investigation. 



4. Reactions Accompanying Adsorption. 



Thermal waters from Bareges' springs reddrn blue Congo by 

 warming. 



This may be accounted for by supposing that basic gels exist in 

 the thermal waters, which adsorb the acid of Congo red at ordinary 

 temperature, without change in the color, which remains blue; 

 on warming, chemical reaction takes place and a salt of Congo red 

 is formed, a red color appearing. At the same time, an insoluble 

 blue acid of the Congo is precipitated, which may again yield 

 interesting adsorbent effect. 



Such reactions have called for the attention of numerous investi- 

 gators and Wedekind and Rheinboldt conclude that adsorption 

 effect may often precede chemical union, which seems specially 

 true of biochemical reaction as was observed for iron depositing 

 bacteria. 



Summary. 



1. The compounds, in living cells or tissues, are colloids 

 displaying selective adsorption effect. 



The constituents of cell walls and most granules in the cytoplasm 

 are base-adsorbent colloids; they compete for bases, each with 

 the other, and with the basophilous colloids in the habitat. 



The constituents of nucleoplasma are generally acid-adsorbent, 

 but may become base adsorbent in diseased cells. 



Cellulose, an acid-adsorbent colloid, is widely distributed in 

 plant cells and may exert powerful adsorption towards acids. 



2. Adsorption effect may be preliminary to biochemical 

 reaction, as is probably the case for iron depositing bacteria. 



3. Competition for bases may result in serious loss of bases in 



