506 



SCIENCE 



[N. S. Vol. XLIII. No. 1110' 



is to be sought in some type of physical-chem- 

 ical equilibrium that permits the permeability 

 aboYe and below a norm to vary reversibly 

 within definite limits. We have pointed out 

 above that there is in every colloidal system an 

 aggregation or solution equilibrium between 

 disperse phase and dispersion medium. The 

 colloids at the surface of the cell are no ex- 

 ception to this rule. The continued action of 

 a liquefying agent at the cell surface pro- 

 duces a marked increase in permeability and 

 eventually death by irreversible liquefaction. 

 On the other hand, a coagulating agent, i. e., 

 an agent that increases the aggregation of 

 the disperse phases of the surface colloids, 

 produces at first a decrease in permeability, 

 but, if the action be sufficiently prolonged, the 

 disperse phases separate out from the disper- 

 sion medium and death follows as a result of 

 surface coagulation. Once the disperse phases 

 have begun to separate from the dispersion 

 medium, the fluidity of the cell surface ap- 

 proaches that of the pure dispersion medium 

 which obviously involves a tremendous in- 

 crease in permeability. Thus cell death, 

 whether by irreversible surface liquefaction 

 or by irreversible surface coagulation, invari- 

 ably involves an increase in the permeability 

 of the cell. The term " cytolysis " has been 

 loosely applied to cover both eases, though 

 from a physical-chemical standpoint we are 

 dealing with antithetical processes. 



The degree of aggregation of the surface 

 colloids, i. e., the degree of intimacy of rela- 

 tion between disperse phases and solvent ap- 

 pears, upon last analysis, to be the critical 

 condition upon which depends the continuation 

 of the cell as a living system. The degree of 

 aggregation of the disperse phases at the sur- 

 face of the ceU is directly dependent upon 

 their solubility in the dispersion medium. 

 This solubility is determined (1) by the con- 

 centration, nature and number of electrolytes 

 or organic substances occurring in the liquid 

 phase, and (2) by the temperature of the whole 

 system. We may, therefore, say: (A) at the 

 surface of every cell there is a solution equi- 

 librium, a vital equilibrium, between disperse 

 phases and solvent; (B) the permeability of 



the cell is determined by the maintenance or 

 shifting of the vital equilibrium. 



We may now summarize the foregoing con- 

 clusions as follows : 



1. In the limiting colloidal system of every 

 cell, whether in the form of a differentiated 

 membrane or not, there exists an equilibrium 

 between disperse phases and dispersion me- 

 dium. 



2. A shifting of this equilibrium in the di- 

 rection of greater dispersion causes an in- 

 creased permeability of the cell surface, since 

 the fluidity of the system is increased, the 

 viscosity of the surface is lowered, and a more 

 rapid diffusion occurs across the surface both 

 into and out of the cell. 



3. A slight shift of this equilibrium in the 

 direction of increased aggregation involves a 

 solidifying action at the surface, an increased 

 viscosity, a slower rate of diffusion across the 

 surface and a consequent decrease in permea- 

 bility. 



4. A considerable shift of this surface equi- 

 librium in the direction of increased aggrega- 

 tion (insolubility of the surface colloids) in- 

 volves a decrease in the degree of intimacy 

 between disperse phases and solvent ; the fluid- 

 ity is suddenly increased and diffusion across 

 the surface is correspondingly facilitated. 



5. The critical condition of any cell surface, 

 upon which eventually depends the continua- 

 tion of the cell as a living system, is the state 

 of aggregation of its surface colloids, i. e., the 

 relation of disperse phases to dispersion me- 

 dium. We may, therefore, speak of a solution 

 equilibrium, a vital equilibrium at every cell 

 surface, reversible within definite limits, the 

 overstepping of which produces death by sur- 

 face liquefaction, on the one hand, or by sur- 

 face coagulation, on the other. 



We have thus far considered the cases in- 

 volving the effects of single electrolytes upon 

 the surface colloids of cells. We shall now 

 briefly consider the physiological effects (1) 

 of combinations of electrolytes and (2) of ele- 

 vation of temperature. 



In any combination of electrolytes it is clear 

 that if it were possible exactly to compensata 

 the dispersion effect of one constituent or 



