IDIOSYNCRASY AND ANAPHYLAXIS 551 



quently the hypersensitiveness may extend to other tissues. As stated above, 

 under some circumstances these localized reactions may appear negligible as 

 compared with the general reactions which take place ; this occurs, for 

 instance, when a large quantity of the offending substance, such as a foreign 

 serum, enters into the circulation. 



The condition with which we have to deal in idiosyncrasy is evidently very 

 similar to that observed in experimental anaphylaxis produced in animals by 

 repeated injections of substances of a protein character. Opie has made it 

 very probable that local anaphylactic reactions, as those characteristic of the 

 Arthus phenomenon, are due to a local interaction between the antigenic 

 protein and the precipitin which developed in response to the antigenic pro- 

 tein. The presence and significance of precipitins in this reaction has recently 

 been confirmed by Cannon, who used more accurate quantitative methods for 

 the determination of circulating precipitin and thus demonstrated the 

 parallelism between the amount of precipitin formed and the strength of the 

 allergic reaction. However, at present the possibility cannot as yet be entirely 

 excluded that also other types of antibodies may be involved in anaphylactic 

 phenomena. Anaphylactic shock corresponds to the general reactions noted 

 in some cases of serum disease ; the local status of anaphylaxis, either in the 

 skin as seen in the Arthus phenomenon, or in the intestines (Schultz), uterus 

 (Dale), or blood vessels (Friedberger), corresponds to the types of local 

 hypersensitiveness as they become manifest in various cases of idiosyncrasy. 

 However, the anaphylactic shock of the guinea pig, which is the animal most 

 commonly used in the study of this condition, depends mainly upon a 

 localized hypersensitiveness of the bronchial musculature; but there may also 

 be associated changes in the nervous and circulatory systems. If we except 

 some minor variations, there are two main differences which have led to a 

 separation of the state of idiosyncrasy from that of anaphylaxis : ( 1 ) While 

 in anaphylaxis the abnormal reaction indicating hypersensitiveness can be 

 traced to a previous sensitization by the same substance which subsequently 

 elicits the reaction, in idiosyncrasy the reaction may be induced by a substance 

 with which the body has apparently not previously been in contact; (2) 

 while in anaphylaxis we have to deal with a hypersensitiveness to protein 

 substances, in the case of idiosyncrasy the active substance may be of a 

 much simpler character. But in some instances of idiosyncrasy the chemical 

 character of the active substance is unknown, and it is possible that we may 

 have also, in idiosyncrasy, sometimes to deal with protein substances. (3) In 

 general, anaphylaxis is a well defined condition of hypersensitiveness which 

 may be experimentally produced in animals, idiosyncrasy is a condition of 

 hypersensitiveness which apparently occurs spontaneously in man. In regard 

 to the first of the differences between these two states mentioned, there is 

 much evidence of a clinical as well as of an experimental character, which 

 suggests that also in idiosyncrasy in man a previous but unsuspected sensitiza- 

 tion may often have taken place. In some of these instances the sensitization 

 may even have occurred during intrauterine life by way of the placenta, in 

 others it may become manifest only a considerable time after contact of the 



