36 THE PRINCIPLES OF IMMUNOLOGY 



tation indicates that the main source of antibody formation was 

 removed or the absorption of the antigenic substances entirely 

 stopped. Forsmann and Lundstrom studied the curve of pro- 

 duction of botulinus antitoxin following single intravenous or 

 subcutaneous injection of the toxin. The curve following the 

 subcutaneous injection reached its highest level on the fifteenth day, 

 while that following the intravenous injection attained the maximum 

 on the tenth day. It must be inferred that the subcutaneous method 

 of injection introduces the factor of slow absorption, but it is also 

 possible that some local factor may enter into the phenomenon. 

 Immunization of horses with diphtheria toxin results in a greater 

 yield of antitoxin when the horses are injected subcutaneously, but 

 this does not necessarily prove a local production of antitoxin at the 

 site of inoculation. Local cellular participation in immune reactions 

 will be discussed further in the chapter on hypersusceptibility. 

 There is little doubt that local reactions are of significance and that 

 absorption may be influenced by local changes. The production of 

 circulating antibodies in any considerable amounts undoubtedly re- 

 quires more extensive cellular activity than that about the site of 

 local inoculations. 



