124 THE THEORY OF IONS 



him to explain his views of immunity, does not satisfy 

 all the conditions. He has utilised the fact that 

 the affinity of toxin for antitoxin, and the toxicity 

 of toxins, vary independently of each other to sup- 

 port the idea that each contains a toxophore and a 

 haptophore group, which supply the materials for 

 the reaction. But Arrhenius, Gruber, Pauli, and 

 others, who seek for an explanation of the facts by 

 the light of the ionic theory, consider that toxin and 

 antitoxin consist of a mixture of compounds which 

 have a weak affinity for each other ; and that 

 Ehrlich's assumptions are not supported by the facts 

 of colloidal chemistry. 



It is through a study of colloidal chemistry that 

 we may also expect to find an explanation of extra- 

 cellular phenomena such as the development of .car- 

 tilage and bone, and the precipitation of crystalline 

 substances in these and other tissues. The nucleus 

 of the question consists of the fact that we are 

 dealing on the one hand with the simple process 

 of crystallisation, and on the other with the forma- 

 tive influence of the cells and forces destined to act 

 upon them. The colloids constitute an excellent 

 means of keeping slightly soluble salts in solution, 

 under certain circumstances, by uniting with the 

 ions of the salts to form aggregates which in the case 

 of protein are not necessarily precipitated (vide ante). 

 If however through some influence, such as meta- 

 bolism, the dissolving protein is destroyed, a pre- 

 cipitation of the colloidal material may occur. 

 Crystals being once formed may serve for centres of 

 continued crystallisation. It is in such a conception 

 of the vital activities of the cell and cystallisation 



