90 ADSORPTION 



brought forward evidence in favour of his view to which this 

 objection can hardly apply. It will not be discussed here, as it 

 involves certain questions concerning serum haemolysins which 

 have not yet been discussed. 



Bordet's theory supplies an explanation, though hardly an 

 adequate one, of the negative phase. We have already seen that 

 when an animal is producing antitoxin an injection of toxin will 

 cause a fall in the antitoxic value of the serum far greater than 

 can be accounted for by the neutralization effected by the toxin 

 injected : it may be 2,000 times as great, or more. If we assume 

 that the combination does not take place in obedience to the laws 

 of multiple proportions, we can imagine that it may go on very 

 differently in the body, and that in that situation a small amount 

 of toxin may neutralize a large amount of antitoxin. But it is 

 very difficult to believe that this is the true explanation, for it 

 would involve an increase of the neutralizing power of the toxin 

 to 2,000 times that which it has outside the body an increase 

 which certainly seems improbable. Further, we have been asked 

 to imagine a molecule of antitoxin spreading itself out and 

 weakening many molecules of toxin, and we are now asked to 

 imagine a molecule of toxin dividing itself amongst 2,000 molecules 

 of toxin, and completely neutralizing them. 



The last conception which we have to consider is that of Biltz, 

 which approaches very closely to Bordet's. Starting with the 

 idea that toxins and antitoxins are both colloids, he attempts to 

 show that their union is analogous to adsorption rather than to 

 an ordinary chemical union. 



Adsorption is a process akin to solution, and does not necessarily 

 involve a chemical union between the two substances which take 

 part in it. It may take place between colloids and colloids, or 

 between colloids and crystalloids, and in other ways. The two 

 substances taking part in the process are found to be electrically 

 positive and negative (as shown by their moving to the cathode 

 or anode in an electric field) ; thus a colloidal solution of silicic 

 acid (which is negative) is precipitated slowly by K 2 SO 4 , which 

 has a feeble positive charge ; more rapidly by CuSO 4 , which has a 

 stronger one ; and immediately by A1 2 (SO 4 ) 3 , which has a stronger 

 one still. 



Biltz and his collaborators started with the idea that toxins and 

 antitoxins are both colloids. They attempted to find the electrical 

 nature of tetanus toxin by electrolysis, but found that it was 



