33 COLLOIDAL CHEMISTRY 



kept in contact for two hours, no tetanus is produced, in spite of 

 the local action of the adrenalin. This appears to harmonize best 

 with the colloidal theory. The interactions of colloids of opposite 

 sign and the precipitation of colloids by electrolytes may be 

 reversible if the conditions are changed early, but the compounds 

 formed gradually become more and more stable. But if the con- 

 tinuation were that of two substances of strong chemical affinity 

 we should expect it to be stable from the first, and if it followed 

 the laws of mass reaction it would be reversible, no matter how 

 long it had stood. 



There appears to be no crucial experiment by which the truth 

 of these three theories can be tested. The arguments brought 

 forward by the upholders of each involve the study of the exceed- 

 ingly complicated laws connected with the true relations and 

 completeness of the reactions, and involve advanced mathematical 

 consideration. It is, however, doubtful whether the processes are 

 measurable with the accuracy required in the investigation of 

 these complicated formulae, and in some cases very slight altera- 

 tion of the observed results would render the facts explicable on 

 a theory other than that in support of which it was adduced. At 

 the present time the balance of the evidence appears to be decidedly 

 in favour of the colloid hypothesis. 



