384 INFECTION AND IMMUNITY. 



relate the phenomena of anaphylaxis with other 

 processes of immunity. 



Like other processes of immunity anaphylaxis 

 may be classified as natural and acquired; and, 

 again, acquired anaphylaxis may be active, in 

 which the process results from a reaction on the 

 part of the tissue cells, or may be passive result- 

 ing from the introduction of ready-made sub- 

 stances into the body. 



Aim i?vi tur - al ^ ^ as ^ een ^ on known that, as noted by 

 Horwitz, Schofield, Doerr, and others, certain in- 

 dividuals are unusually affected by the ingestion 

 of eggs, crabs, flesh, pork, etc. The symptoms 

 are variable, but there is often nausea, fever, colic, 

 and exanthemata. It is of course to be questioned 

 as to whether such hypersusceptibility is really 

 natural or acquired by early sensitization. Scho- 

 field reports such a case of hypersusceptibility to 

 egg which disappeared after repeated increasing 

 doses of egg taken in pills, using minute amounts 

 to begin with. Such hypersusceptibility has been 

 long known under the name idiosyncracy. The 

 idiosyncracies to proteins, however, should be dis- 

 tinguished from those in which known chemical 

 substances, such as mercury or salicylic acid, are 

 concerned. 



Active anaphylaxis has been studied in a variety 

 of mammals- and fowls, and substances which 

 correspond to those concerned in immunization 

 have been demonstrated. 



It will be well to take up these various factors, 

 and after a discussion of their nature, it will be 

 easier to understand the theories concerning the 

 mechanism of their action. 



