CHEMICAL NATURE OF ANTITOXINS 475 



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. It 

 would, however, be out of place to discuss at length the opposing 

 views, and we accordingly simply state the facts ascertained. 

 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 ; the important fact is that 

 in the nervous system certain molecules have an affinity for the 

 toxin. 



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. 

 This will be discussed below in connection with Ehrlich's theory 

 of passive immunity. We may conclude by saying that anti- 

 toxin is probably represented by molecules normally present in 

 the cells or (more rarely) in the fluids of the body. 



Of the chemical nature of antitoxins we know little. From 

 their experiments C. J. Martin and Cherry deduce that while 

 toxins are probably of the nature of albumoses, the antitoxins 

 probably have a molecule of greater size, and may be allied to 

 the globulins. Hiss and Atkinson have also come to the con- 

 clusion that antitoxin belongs to the globulins. They found 

 that the precipitate with magnesium sulphate from anti- 

 diphtheria serum contained practically all the antitoxin, and that 

 any substance obtained which had an antitoxic value gave all 

 the reactions of a globulin. They also found that the per- 

 centage amount of globulin precipitated from the serum of the 

 horse increased after it was treated in the usual way for the 

 production of antitoxin. Such a supposed difference in the 

 sizes of the molecules might explain the fact, observed by 

 Fraser and also by C. J. Martin, that antitoxin is much more 

 slowly absorbed when introduced subcutaneously than is the case 

 with toxin. 



Antitoxin, when present in the serum, leaves the body by 



