Mat 28, 1920] 



SCIENCE 



527 



with electrolyte solutions (formation of pre- 

 cipitation-tubules of zinc or iron ferricyanide, 

 rust-patterns, etc.)- Transmission-effects in 

 protoplasmic systems (i. e., in nerve, etc.) 

 may be closely paralleled by processes of 

 chemical transmission or distance-action in 

 film-covered metallic systems, like passive iron 

 in nitric acid or mercury in hydrogen per- 

 oxide. Many cell-processes are associated with 

 changes in the osmotic properties or per- 

 meability of the protoplasmic surface-films or 

 plasma-membranes. The high development of 

 surface layers or membranes is in fact a long- 

 recognized structural peculiarity of living 

 matter. The prevalence of the cellular type 

 of organization is in itself evidence of the 

 fimdamental importance of this condition. 



These general facts indicate strongly that 

 for the purpose of gaining further insight 

 into the physico-chemical constitution of 

 living matter a more thorough and detailed 

 study (1) of the general properties of surfaces 

 (their structure, tension, electrical properties, 

 etc.), (2) of the layers of material formed 

 at surfaces (surface-films, etc.), and (3) of 

 phenomena dependent on surface conditions 

 (adsorption, catalytic effects, flocking and pep- 

 tization of colloids, etc.), is all-essential. Prob- 

 ably the purely physical or chemical investi- 

 gation of these problems will best be under- 

 taken by students trained in the methods of 

 physics and physical chemistry. Data or prin- 

 ciples so obtained can then be applied to bio- 

 logical or medical problems by those specially 

 qualified to deal with such problems. 



There is much evidence that living proto- 

 plasm is essentially emulsion-like in its fun- 

 damental physical constitution; and it is 

 known that the properties of emulsions are 

 largely determined by the presence of inter- 

 facial films and by the electrical and other 

 conditions resident at the phase-boundaries. 

 The general physical and chemical conditions 

 affecting the stability and properties of emul- 

 sion-systems are thus in large part identical 

 with those affecting the stability and proper- 

 ties of living protoplasm. As is well known, 

 emulsions are mixtures of two (or more) 

 mutually insoluble liquids, of which one is in 



a state of fine division and dispersed through- 

 out the other; for stability a third substance 

 (e. g., soap), forming a surface-film between 

 the two phases, is usually required. Recent 

 work has shown that the properties of oil- 

 water emulsions may be made to vary in a 

 remarkable manner by varying the salt-con- 

 tent of the system, and that these changes 

 depend upon the solubilities of the soaps 

 formed and upon their surface-activity. Many 

 surprisingly close parallels between the effects 

 of different combinations of salts on emulsion- 

 systems and on living protoplasmic systems 

 have been demonstrated. It is well known 

 that the presence of inorganic salts in definite 

 proportions is essential to the normal activity 

 of most living cells. Such results, therefore, 

 indicate the importance of initiating and ex- 

 tending researches which will have as their 

 object the determination of the relation be- 

 tween the soluble substances (both electrolytes 

 and non-electrolytes) present in emulsion- 

 systems and the general physical properties 

 and behavior of such systems. Light may 

 thus be thrown upon the general properties of 

 protoplasm (mechanical properties, structure, 

 permeability, electrical properties), in so far 

 as these properties are determined by the 

 emulsion-like constitution of the system. 



This emulsion-structure, however, furnishes 

 only the field or substratum in which the 

 essential chemical reactions (or metabolism) 

 of the living protoplasm proceed. The special 

 nature of these chemical processes determines 

 the special properties and behavior of the 

 protoplasmic system. Hence the relation of 

 the film-pervaded or emulsion-like structure 

 of protoplasm to the special type of chemical 

 activity exhibited by the living system should 

 be thoroughly studied and investigated. 

 There are many indications that the extra- 

 ordinary chemical capabilities of living mat- 

 ter are dependent upon the extent of its sur- 

 face development: i. e., that the influence of 

 protoplasm in inducing chemical reactions not 

 found elsewhere is essentially the residt of the 

 special predominance of surface influences of 

 a peculiar kind. And since the sensitivity of 

 living matter to the electric current is one of 



