SUPERSENSITIVENESS OR ANAPHYLAXIS 561 



With regard to the mechanism underlying the phenomena 

 described, practically all observers are agreed that there is a 

 profound affection of the nervous system ; but it is still an open 

 question as to \\lirtlnT the severe and practically simultaneous 

 affections of the other systems are merely secondary, or whether 

 they are independently produced by some change common to 

 all. A great fall in the blood-pressure is an important 

 plu'iiomenon, and is due chiefly to a general vaso-dilatation ; 

 and it has been pointed out by Auer and Lewis that in the 

 case of guinea-pigs there occurs a spasm of the muscle fibres in 

 the fine bronchi and alveolar passages, the chest-wall being fixed 

 in full inspiration at the time of death. Besredka has shown 

 that the fatal symptoms are more rapidly produced in an 

 anaphylactic animal and with a smaller dose of serum, when 

 the injection is made directly into the brain, than by any other 

 method. Further, seeing that a single dose of horse serum is not 

 toxic to the guinea-pig, and that an interval of several days 

 must elapse before anaphylaxis is established, the majority of 

 observers consider that at least two substances are concerned, 

 one of which is contained in normal horse serum, whilst the 

 other is developed in the guinea-pig in response to the presence 

 of the first or of some other substance after the manner of an 

 anti-substance. To this newly developed substance the name 

 of " anaphylactic reaction-body " is often given. The phenomena 

 thus depend upon the co-operation of the reaction-body with a 

 substance or substances in the horse serum, and a rapid union 

 of the two, probably within the nerve-cells, brings about the 

 anaphylactic shock. Passive anaphylaxis would thus be due to 

 the transference of the reaction-body to a fresh animal, and the 

 interval necessary before the second injection might depend 

 upon the time required for the reaction-body to accumulate in 

 .sufficient quantity within the nerve-cells. 



lU'sivdka considers that the sensitising and the toxic factors 

 in the horse serum are not one and the same. He finds that 

 serum heated to a certain temperature may still have the power 

 of inducing the condition of anaphylaxis, but has lost the power 

 of bringing about the toxic phenomena when injected into an 

 anaphylactic animal. Gay and Adler similarly find that the 

 sensitising substance (anaphylactin) is contained in the 

 i-ii^lobulin fraction of the serum while the other is not. 

 llrsrcdka accordingly puts forward the view that in the horse 

 si-rum there are two substances or rather factors, namely, 

 sen8ifii/i*''it!/'-/i. which is thermostable, and anti-sensibilisin, 

 which is thermolabile. When the serum is injected the former 



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