532 IMMUNITY 



their experiments C. J. Martin and Cherry deduced 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. 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. 

 Hiss and Atkinson also came to the conclusion 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 ; 

 and this result has been confirmed by others. They also found 

 that the percentage amount of globulin precipitated from the 

 serum of the horse increased after it was treated in the usual 

 way for the production of antitoxin. Ledingham observed an 

 increase of globulin during the process of immunisation of a 

 horse which yielded a high-grade antitoxic serum, and he ascer- 

 tained that while this increase was more on the part of the 

 euglobulin than of the pseudoglobulin fraction, most of the 

 antitoxin was contained in the latter. 



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

 various secretions, and in these it has been found, though in 

 much less concentration than in the blood. It is present in the 

 milk, and a certain degree of immunity can be conferred on 

 animals by feeding them with such milk, as has been shown by 

 Ehrlich, Klemperer, and others. Klemperer also found traces of 

 antitoxin in the yolk of eggs of hens whose serum contained 

 antitoxin. Bulloch also found in the case of hseinolytic sera 

 (vide infra) that the anti-substance ("immune-body ") is trans- 

 mitted from the mother to the offspring. 



Antibacterial Serum. The stages in the preparation of 

 antibacterial sera correspond to those in the case of antito'xic 

 sera, but living, or, in the early stages, dead cultures are used 

 instead of toxin separated by filtration, and in order to obtain a 

 serum of high antibacterial power a very virulent culture in large 

 doses must be ultimately tolerated by the animal. For this 

 purpose a fairly virulent culture is obtained fresh from a case of 

 the particular disease, and its virulence may be further increased 

 by the method of passage. This method of obtaining a high' 

 degree of immunity against the microbe is specially applicable 

 in the case of those organisms which invade the tissues and 

 multiply to a great extent within the body, and of which the 

 toxic effects, though always existent, are proportionately small 



