104 ANTIGENS AND ANTIBODIES 



and suppose that during the interaction between the lysin and its 

 antigen, at the time of the second injection, highly poisonous 

 intermediary products are formed to which the peculiar symptoms 

 are in turn due. 



Anaphylaxis. As the injected animal has evidently become more 

 sensitive to the action of the foreign albumin than it was before the 

 first injection, which usually does not give rise to any serious symp- 

 toms, Richet suggested the term anaphylaxis to express this condition 

 of hypersusceptibility, in contradistinction to prophylaxis, diminished 

 susceptibility or immunity, in the older sense of the word. This 

 term has now been generally accepted, and the more or less threaten- 

 ing symptoms which follow the second injection are accordingly 

 spoken of as the anaphylactic shock. French writers, more particu- 

 larly, refer these symptoms to a special anaphylactic reaction product 

 which they term anaphylactin. v. Pirquet, as we have already seen, 

 has introduced the non-committed term allergia to denote the changed 

 mode of reaction on the part of the injected animal (no matter what 

 antigen has been used) and speaks of the antigenic substances as 

 the allergens and the reaction products as the corresponding ergins. 

 According to his ideas, anaphylaxis is thus merely one form in which 

 the general allergia can express itself. In a subsequent chapter we 

 shall have occasion to deal with this problem in greater detail, and 

 we hope to show that the antibodies which are especially involved 

 in the anaphylactic reaction, play an important role in the symptom- 

 atology of many diseases. 



The brief survey of the manner in which the animal body responds 

 to the parenteral introduction of foreign cells and cell derivatives, 

 which has just been given, imperfect and condensed though it be, is 

 probably sufficient to show that a field of work has been opened up 

 which offers a most alluring perspective to the investigator, both in 

 medicine and general biology. During the few years that it has 

 been tilled, the returns have already been wonderful in their diver- 

 sity and value, and we have every reason to suppose that a great deal 

 of the future progress of medicine will lie in this direction. We have 

 already a host of experimental facts which only await their proper 

 interpretation, before they will become important stepping stones 

 toward still more important findings. Among the many able investi- 

 gators who are closely associated with progress along these lines, one 



