154 ANAPHYLAXIS 



antianaphylactic, so that it can be injected even after a very 

 brief interval with possibly a hundredfold larger dose of the 

 antigen without any deleterious results (see also Mechanism of 

 Antianaphylaxis) . 



Anaphylactogens. Subsequent investigations have then shown 

 that an anaphylactic reaction can be called forth by the injection 

 not only of blood-serum, but also of milk, albuminous urine, sweat, 

 bile, red cells, extracts of various normal tissues as well as of neo- 

 plasms, 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 noteworthy 

 that this in itself need not be toxic to the slightest degree. It seems, 

 indeed, as though true toxins could not produce anaphylaxis, 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 somewhat; this is 

 what actually occurred in the case of Richet's actinocongestin, 

 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 anaphyladogens, allergens, or 

 sensibilisinogens . 



Serum Sickness. It was next 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 of 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- 



