302 AGEICULTUEAL AND INDUSTEIAL BACTEEIOLOGY 



been thus sensitized to the protein is said to be in a condi- 

 tion of hypersusceptibility or anaphylaxis. 



The anaphylactic reaction is very specific. A guinea pig 

 injected with one kind of protein does not become sensi- 

 tized thereby against other kinds of protein. 



Other species of animals than the guinea pig may be 

 similarly sensitized by the parenteral introduction of pro- 

 tein, that is by an injection or introduction of protein by 

 some means other than through the normal channel of the 

 alimentary tract. The symptoms developed as a result of 

 the second injection into these other animals may differ 

 materially from those exhibited by the guinea pig. 



Examples of Natiiral Anaphylaxis. — ^It vsras noted above 

 that occasionally individuals may develop sensitiveness to 

 the presence of particular proteins without any intentional 

 preliminary sensitization. Such, for example, is the sensi- 

 tization of individuals to the pollen of certain plants. In 

 the United States in many localities the rag weed pollen 

 during the months of August and September causes intense 

 irritation of the mucous membrane of the respiratory tract 

 of those individuals said to have the disease hay fever. Just 

 how such individuals became sensitized, it is difficult to 

 ascertain. 



Certain individuals become sensitized to the proteins 

 specific for particular animals. There are persons, for 

 example, that cannot be in the vicinity of a horse or inhale 

 the scurf from the skin of the horse without being subjected 

 to an attack of asthma. In fact many types of asthma are 

 undoubtedly due to the inhalation of particles of dust con- 

 taining proteins or other substances to which the individual 

 has in some way become sensitized. Individuals who have 

 thus become sensitized to proteins will show the character- 

 istic reaction in a variety of ways. If an extract of rag 

 weed pollen be rubbed vigorously into the skin of a person 

 subject to hay fever caused by this particular type of 



