PHYSICAL FORCES INVOLVED IN BIOLOGICAL ACTIVITIES 1 71 



The possible effect surface tension may have upon the outer layer of 

 protoplasm constituting a cell and in the formation of a membrane, 

 its relation to nutritional functioning and in cellular movements, its 

 suggestiveness in connection with form and its probable importance 

 with alterations of various kinds render it a topic of prime import- 

 ance although its values are very much dimmed by incomplete 

 knowledge. 



ADSORPTION 



Spongy platinum has the power to take up considerable quantities 

 of hydrogen gas and also oxygen gas into its mass; charcoal takes color- 

 ing material from solutions; it also takes up gases; platinum black takes 

 up acetic acid; calcium carbonate takes up sodium nitrate. When 

 substances are so taken they are said to be adsorbed. This power seems 

 to be resident in the adhesive forces of the extensive surfaces which 

 exist through the multiplicity of particles in the substance as in charcoal. 

 It has been defined as the local concentration or condensation of dis- 

 solved substances at the interface between two phases. For instance, 

 the interface existing between the dispersoid phase and dispersion 

 means intensifies the surface action to such an extent that there is a 

 concentration, a condensation. Reactions are apparently accelerated. 

 The contact of hydrogen and oxygen in spongy platinum produces 

 water. The action many times is that of catalysis as the oxidation of 

 alcohol to acetic acid by platinum black. The adsorbing substance 

 does not seem to enter into the chemical reaction which may occur but 

 may be recovered intact. 



These reactions are influenced by temperature, pressure, electric 

 forces and nature of the substance. 



By this phenomenon of nature soluble salts are held back in soils 

 and not washed away by rains. The action of certain disinfectants is 

 explained by the deposition or concentration on the surfaces of micro- 

 organisms; the reaction of toxin with antitoxin simulates adsorption 

 phenomena more closely than mass action; the sensitization of bacteria 

 by opsonins and the ingestion by leucocytes also resemble adsorption 

 acts; the peculiar reactions of enzymes are regarded as similar to ad- 

 sorption; the formation of a membrane upon exposed protoplasm in 

 the case of a crushed protozoon also appears to be the result of the 

 adsorptive action of certain substances. 



