FROM THE SMALL INTESTINE 631 



antitoxic action of a calcium salt appears to be due to its power 

 of reducing the permeability of the membrane to the toxic salt. 

 How these changes in permeability are brought about we do not 

 know, any more than we know whether or not permeability is a 

 chemical or physical phenomenon, (c) Liquefaction of the cilia 

 of larvae is observed to take place in some solutions and to be 

 prevented by the presence of other salts. Besides these gross 

 toxic changes, however, it is likely that ions can influence bio- 

 plasm in many other ways, such as alterations in the state of 

 colloidal aggregation, alterations of surface tension, &c., and perhaps 

 chemically ; but these are largely theoretical and cannot be 

 discussed. 



Thus far we have dealt entirely with the action of ions on 

 living matter. But it must not be thought that their field of 

 action is confined to bioplasm, and that because ionic action may 

 be demonstrated to have taken place, it is any proof that the 

 material, on which it is acting, is living. Hardy and others have 

 demonstrated the power of solutions of electrolytes to produce 

 coagulation of colloidal solutions. It is a matter of secondary 

 importance whether the coagulative power of ions is related to 

 their valency as opposed to their ionic potential. The results 

 suggest that the power of salts to alter the permeability of cells 

 and the physiological activity of bioplasm may be connected in 

 part with a power to alter the physical, perhaps electrical, con- 

 dition of the protoplasmic colloids. Cole and others have 

 investigated the action of ions upon the activity of unorganised 

 ferments. Cole came to the general conclusion that the activity 

 of a ferment is stimulated by anions and depressed by cations, 

 the effect of the ions being determined by their actinising power. 

 His results have been confirmed and extended by McGuigan, who 

 concluded that the inhibitory power of any salt is inversely 

 proportional to the sum of the solution tensions of its ions ; a 

 result which is identical with that arrived at by Mat hews for 

 the action of ions on nerve. Neilson and Brown have shown 

 that the catalytic decomposition of hydrogen peroxide by plati- 

 num black is stimulated by anions and inhibited by cations. 

 This action of ions upon unorganised ferments must be of great 

 importance in relation to experiments on absorption. For, 

 during absorption, the products of digestion undergo change by 

 ferments ; and further, it is now thought that many of what used 



