146 ANAPHYLAXIS 



neoplasms, the contents of echinococcus cysts, extracts of lower 

 animals or of vegetable organisms, including bacteria, etc., in short 

 by any substance of albuminous character, and it is especially note- 

 worthy that this in itself need not be toxic to the slightest degree. 

 It seems, indeed, as though true toxins could not produce anaphyl- 

 axis, and that if this apparently occurs, it is due to contaminating 

 albuminous substances. This, however, does not preclude the 

 possibility that toxic albumins may give rise to the reaction, and we 

 have seen, as a matter of fact, that Richet's original experiments 

 were carried out with such material. In such an event, of course, 

 the toxic character of the albumins may blur the picture some- 

 what; this is what actually occurred in the case of Richet's actino- 

 congestin, and no doubt led to his assumption that the extract 

 contained both a toxic (anaphylactic) substance and a non-toxic 

 immunizing (prophylactic) principle. 



Collectively those substances which are capable of rendering an 

 animal anaphylactic are spoken of as anaphylactogens, allergens, or 

 sensibilisinogens. 



Serum Sickness. It was then shown that any animal may be 

 rendered anaphylactic, but that the mode and intensity of the 

 reaction is not the same in all. The most susceptible animal is 

 evidently the guinea-pig, and we have already seen the manner in 

 which it reacts to the introduction of horse serum. In man the 

 same antigen leads to those symptoms which collectively are spoken 

 of as serum sickness, the most common of which are the occurrence 

 of fever, of exanthemata, and swelling of the joints. In dogs we 

 note great restlessness, crying out aloud, and marked fall in blood 

 pressure, non-coagulability of the blood, and leukopenia. In goats 

 extreme myosis has been observed. 



Passive Anaphylaxis. Most important further is the observation 

 that the anaphylactic reaction product (the anaphylactin or sensi- 

 bilisin of the French; the allergin of v. Pirquet) can be transferred 

 from one animal to another, in a manner quite analogous to the 

 production of passive immunity, and writers hence speak of passive 

 anaphylaxis, which may be homologous or heterologous, i. e., it 

 can be transferred to an animal of the same species or to one of a 

 species which is different from the one which was actively sensitized. 

 The discovery of this fact has had important bearings upon our 

 understanding of the mechanism which underlies the production 



