IMMUNITY 221 



scarcely begun to be applied to the study of immunity, and 

 the body-fluids, the toxins, and the antitoxins had not yet 

 been studied from the point of view of their colloidal con- 

 stitution. The phenomenon of adsorption (ad in preference 

 to ab as expressing the idea of attraction or adhesion) is a very 

 general one, and does not depend absolutely on the colloidal 

 state. Bordet therefore, in explaining his conception, pre- 

 ferred to employ the comparison with dyeing processes. The 

 action of antitoxin on toxin appeared to him to resemble, for 

 example, the action of iodine on starch : the immune body 

 which prepares bacteria or cells for the action of complement 

 he regarded as acting after the manner of mordants in dyeing, 

 intermediary substances necessary for the fixing of certain dyes 

 on certain cloths. Thus in haemolysis the union of the 

 immune-body with the blood corpuscle (anti-body H- antigen) 

 forms a combination possessing a greater adsorptive affinity 

 than the normal corpuscle : the complement tends to become 

 precipitated .on the sensitized corpuscle, and the attraction 

 which the latter exerts is more powerful the more heavily it is 

 sensitized.^ n^ 



Inorganic substances present similar phenomena. Water \ 

 runs off a watch glass coated with paraffin without sticking to 

 it, but if the water contains barium sulphate in suspension it 

 wets the paraffin and spreads over it ; this depends on the fact 

 that the surface of the paraffin becomes coated by molecular ^ 

 adhesion with a thin white film of barium sulphate, which ', 

 water can wet ; this film is not removed by rinsing in water, 

 and can only be removed by rubbing. There are even sub- 

 stances which inhibit this fixation of the barium sulphate on 

 the paraffin, just as there are substances which inhibit the 

 fixation of complement by sensitized corpuscles. 



On all the most important points of the question of the 

 toxin and antitoxin combination, the physical theory is the 



^ Those sera which possess the power of inhibiting haemolysis act by 

 keeping the complement in a condition of greater suspension or dissemina- 

 tion in the fluid ; they thus render it more stable, unlike saline solution, 

 which produces a condition of instability in which the complement 

 condenses itself or is precipitated on the attracting sensitized cells. 



