560 IMMUNITY 



serum. It was afterwards shown especially by the researches of 

 Otto and of Rosenau and Anderson that the sensitising agent 

 had really nothing to do with the toxin or antitoxin, but was 

 contained in the normal serum. 



After this brief review we may consider some of the 

 phenomena of serum anaphylaxis, as it is now called. In its 

 study horse serum has been chiefly employed, but other sera are 

 also efficient, and guinea-pigs are the most suitable test animals, 

 though rabbits have also been used ; in the case of mice it is 

 difficult if not impossible to bring about serum anaphylaxis. 

 There is first of all the sensitising injection; a guinea-pig is 

 injected subcutaneously with a minute quantity, e.g. '001 c.c. of 

 horse serum, though even smaller amounts may be sufficient and 

 other methods of injection may also be employed. After a 

 certain number of days, usually twelve as a minimum, anaphylaxis 

 has been established, and the test for this is usually made by 

 injecting subcutaneously 5 c.c. of horse serum. In the ana- 

 phylactic animal severe symptoms occur ; restlessness and hyper- 

 algesia are followed by evidence of collapse, the temperature falls 

 markedly, the heart's action becomes weak and the respiration 

 embarrassed ; finally death may occur. The intravenous injec- 

 tion of a smaller amount of serum brings about the same result 

 more rapidly. It is to be noted that anaphylaxis has the 

 character of specificity, apparently within corresponding limits 

 to immunity (p. 521); 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 ana- 

 phylactic, so that the characteristic symptoms appear in it when 

 the test amount of horse serum is injected. In most instances 

 an interval of about twenty-four hours must, however, elapse 

 between the injections (Otto) ; if the two injections are made 

 at the same time there is usually no result. Another interesting 

 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 produce a 

 condition of anti-anaphylaxis, that is, to vaccinate against the 

 supersensitive condition. If, for example, the sensitising dose of 

 horse serum is injected, and then before anaphylaxis is established 

 (i.e. sometime before the twelfth day) another injection of a 

 considerable quantity is made, anaphylaxis does not appear, and 

 the animal is non-susceptible to further injections of small closes 

 for a considerable period of time. 



