GENERAL PHYSICAL CONSTITUTION OF LIVING MATTER 37 



A negatively charged colloid can form salts with metals; and it is in 

 harmony with the general facts concerning the solubility of salts, that 

 the latter decreases with the valency of the ion with which the colloid 

 combines. Hardy, Bredig, and many other authors believe, however, 

 that in this case the ions act only through their electric charges. Hardy 

 has recently found that electro-negative globulin solutions are rapidly 

 precipitated by the positive electrons sent out by radium.* It is pos- 

 sible that the radiation, in this case, causes a precipitation only in- 

 directly, while its direct action is a chemical change in the globulin 

 solution. 



If we accept the view of Hardy and Bredig, that we are dealing in 

 the action of sols with an effect of an electrical charge of the ions, we 

 shall do well to adopt Bredig's f explanation of this effect. The sur- 

 face tension at the limit of two media reaches a maximum, when the 

 difference of potential between the two media becomes a minimum. 

 This is due to the fact that the electrical charges are antagonistic to the 

 surface tension. The higher the surface tension between colloidal 

 particle and surrounding liquid, the easier will the slightest agitation 

 cause a clumping of the smaller particles into larger aggregates. Those 

 who hold this view have thus far not yet shown how it happens that 

 the valency of an ion has so great an effect upon the precipitation of 

 the colloidal particles, although each precipitating salt carries equal 

 quantities of positive and negative charges into the solution. 



Not all the colloidal solutions show cataphoresis. Hardy men- 

 tions that globulins which are held in solution by salts do not migrate 

 when a constant current passes through them. 



Life depends upon the existence of these colloidal solutions in the 

 cells. All agencies which bring about a general gelation, bring life 

 to a standstill; and such a standstill is permanent in case irreversible 

 gels are formed, such as originate if proteins are heated. The liquid 

 proteins of our body coagulate at a comparatively low temperature, 

 and this is the reason that at a temperature of about 45 the cells of 

 our body die very rapidly. The heavy metals also transform the 

 proteins of our body into irreversible gels, and this may be a reason 

 why tliey are so poisonous. There are, however, conditions in 

 which the transformation of sols into gels does not lead to death, 

 but to the formation of important morphological structures, e.g. Traube's 

 membranes of precipitation. The astrospheres also originate, accord- 

 ing to the botanist, Alfred Fischer, through a process of coagulation. 

 It is, moreover, possible that a series of manifestations of life in cell- 



* Hardy, Jour, of Physiology, Vol. 29, p. xxx, 1903. 

 f Bredig, Anorganische Fertnente, Leipzig, 1901. 



