568 IMMUNITY 



pelled, on theoretical grounds, to conclude that it is not a newly 

 manufactured substance, but a normal constituent of the living 

 cells which is produced in increased quantity. We have, how- 

 ever, direct evidence of the presence of antitoxin under normal con- 

 ditions, the presence of such being shown by its uniting with 

 toxin and rendering it inert. Normal horse serum, to mention 

 an example, may have a varying amount of antitoxic action to 

 the diphtheria poison, ox-bile has a similar action to snake poison, 

 whilst in the case of other anti-substances such as agglutinins, 

 bacteriolysins, hsemolysins, etc. whose production is governed 

 by the same laws, numerous examples might be given. It is, 

 however, rather to the protoplasm of living cells than to the serum 

 that we must look for the source of antitoxins. In the first place, 

 we have evidence that in the living body bacterial toxins enter 

 into combination with, or, as it is often expressed, are fixed by 

 the tissues presumably by means of certain combining affinities. 

 This has been shown by the experiments of Donitz and of 

 Heymans with tetanus toxin. We have, in such cases, however, 

 no evidence as to where the toxin is fixed beyond that supplied 

 by the occurrence of symptoms. Another line of research which 

 has been followed is to bring emulsions of various organs into 

 contact with a given toxin and observe whether any of the 

 toxicity is removed. This was first carried out by Wassermann 

 and Takaki, who investigated the action of emulsions of the 

 central nervous system of the susceptible guinea-pig on tetanus 

 toxin. They found in this way that the nervous system con- 

 tained bodies which had a neutralising effect on the toxin. 

 For example, it was shown that 1 c.c. of emulsion of brain and 

 spinal cord was capable of protecting a mouse against ten times 

 the fatal dose of toxin. These observations have been confirmed, 

 though their significance has been variously interpreted : and in 

 view of recently ascertained facts with regard to processes of 

 physical adsorption, it is quite possible that this neutralisation 

 of toxin does not represent a specific union as in the case of 

 antitoxin action. We may note, however, that it is not a serious 

 objection, that in certain animals other tissues than that of the 

 central nervous system can combine with tetanus toxin this 

 might take place with or without resulting symptoms. 



It will be seen from what has been stated with regard to the 

 relation of toxin and antitoxin, that the fixation of toxin by the 

 tissues leads up theoretically to the possible production of anti- 

 toxin. In other words, the substance which, when forming part 

 of the cells, fixes the toxin and thus serves as the means of 

 poisoning, may act as an antitoxin when free in the blood, 



