82 PROTOPLASMIC ACTION AND NERVOUS ACTION 



the electrical properties of the particles, a factor which 

 influences their adsorption.^ 



Observations on the relation between the concen- 

 tration of proteins in solution and the degree of their 

 adsorption give many abnormalities, probably referable 

 chiefly to variations in the aggregation state.^ The 

 particles cohere and form larger aggregates which con- 

 dense at surfaces, forming films of modified protein. 

 Such processes are largely irreversible, and chemical 

 change probably also enters as a factor; the changes 

 in the properties of enzymes, dyes, and other colloidal 

 compounds in adsorption are probably to be thus 

 explained. Many cases of abnormal and irreversible 

 adsorption belong here; such abnormalities are especially 

 characteristic of colloids of the emulsoid group. The 

 surface-activity of proteins, and the readiness with which 

 they form films, filaments, and other coherent structures, 

 at the surfaces where they are adsorbed, are undoubtedly 

 properties of great biological importance; and we may 

 assume that in the deposition of proteins in a solid or 

 semi-solid state to form the more permanent structural 

 elements of protoplasm such processes play a chief part. 

 As already indicated, it seems probable that specific 

 adsorption, a process apparently based on the tendency 

 of molecules of similar configuration to cohere or coalesce 

 to form larger aggregates, is the fundamental factor 

 underlying the specificity of growth processes. 



As already pointed out, adsorption may furnish the 

 conditions for many of the chemical reactions in cells; 



^ Cf . Christiansen, cited by Pauli, Colloid Chemistry of Proteins, 

 Philadelphia (1922), p. 89. 



2 Cf. Hober, op. cit., pp. 217 flf. 



