SUPERSENSITIVENESS OR ANAPHYLAXIS 597 



and hyperalgesia are followed by evidence of collapse, the 

 temperature falls markedly, urine and faeces are passed, the 

 heart's action becomes weak and the respiration embarrassed : in 

 fatal cases respiration stops before the heart's action ceases. The 

 intravenous injection of a smaller amount of serum brings about 

 the same result more rapidly. It is to be noted that the 

 minimum amount of serum necessary to bring about the 

 symptoms of fatal anaphylactic shock is much greater, about a 

 thousand times greater, than the original sensitising dose ; and 

 that while anaphylaxis is not fully established till about the 

 tenth day, it occurs gradually, — not by crisis, — as can be shown 

 by disturbance of the temperature at a much earlier period on re- 

 injection of serum. Anaphylaxis has the character of specificity,, 

 apparently within corresponding limits to immunity (p. 561) — 

 that is, it is manifested only on the re-injection of the same 

 protein substance as that used in the first instance. There is 

 also a passive anaphylaxis, as is shown by the fact that if a 

 certain amount of the serum of an anaphylactic guinea-pig be 

 injected into a normal one, the latter becomes anaphylactic, so 

 that the characteristic symptoms appear in it when the test 

 amount of horse serum is injected. In most instances an inter- 

 val of some hours at least must, however, elapse between the 

 injections in the guinea-pig (Otto) ; if the two injections are 

 made at the same time there is usually no result. In the rabbit 

 and dog, however, the symptoms appear almost at once after 

 the two injections. Passive anaphylaxis usually disappears 

 after a few weeks at longest, whereas active anaphylaxis has 

 been observed after more than two years ; here also there is 

 an analogy between anaphylaxis and immunity. Another inter- 

 esting observation has been made, namely, that the young of 

 anaphylactic mothers may also be anaphylactic, and the condition 

 may last for some time after birth. It is also possible to pro- 

 duce a condition of anti-anaphylaxis. If, for example, the 

 sensitising dose of horse serum is injected, and then before 

 anaphylaxis is established (i.e., some time before the tenth day) 

 another injection of a considerable quantity of serum is made, 

 anaphylaxis does not appear, and the animal is non-susceptible 

 to further injections of small doses for a considerable period of 

 time. On the other hand, if anaphylaxis exists, the serious 

 effects may be avoided by the injection of a small dose of 

 serum, insufficient in itself to bring about typical symptoms, 

 and then by the injection of graduated increasing doses. 



With regard to the mechanism underlying the phenomena 

 described, practically all observers are agreed that there is a 



