THE FOCAL REACTION 75 



and will appear in a very simple light if we keep in mind the basic 

 idea that the particular symptom complex under study may be due 

 solely to the activation of an inflammatory focus of exogenous or 

 endogenous origin in. the manner of the "Herd Reaktion." Many 

 of the curious metabolic disturbances at times associated with dia- 

 betes and nephritis can readily be accounted for on such a basis. 

 Even pharmacological study reveals evidence of this same nonspe- 

 cific effect on inflammatory lesions. Thus the commonly observed 

 Jarisch-Herxheimer reaction (the flaring up of syphilitic skin lesions 

 under specific treatment) is an example,* while the activation of a 

 tuberculous lesion after iodid medication is an even older observa- 

 tion. So, too, we may get an ulcerative catarrhal condition when a 

 uremic colitis is carelessly treated with calomel, while Koniger, in 

 a recent paper, has even been able to demonstrate that the anti- 

 pyretics, when given in proper interval doses, all bring about a 

 nonspecific "plasmaactivation" and must therefore be included 

 among those agents potentially capable of bringing about focal re- 

 actions. 



This widening of the concept of the focal reaction makes it of 

 decided importance in the special pathology of internal diseases. 

 Acute conditions may often be nothing more than the exacerbation of 

 heretofore latent processes of definite bacterial etiology or perhaps 

 of a diathesis. On this basis can be explained the fact that children 

 often respond with a severe angina to a fault in the diet; that an ap- 

 pendicitis will become acute following an angina, a remote trauma 

 or an injection of a prophylactic dose of vaccine; that a gastric crisis 

 or lancinating pains will commence after some remote exciting cause 

 or an asthmatic attack occur under the influence of some meteor- 

 ological or climatic alteration. 



In many ways this basis for the immediate etiology of an ap- 

 pendiceal inflammation or the flare-up of a gall bladder seems more 

 rational than the suggestion that we deal with a specific localization 

 of bacteria, so altered in their metabolic demands and peculiarities 

 that they will grow only in certain tissues. This latter hypothesis 

 which Rosenow has developed ignores the fact that in the history of 

 acute inflammatory processes one may note a preceding history of 

 remote trauma or systemic shock of some kind or a metabolic dis- 

 turbance of nonbacterial origin just as often if not more frequently 

 than a history of a preceding infection. 



The Diphasic Character of the Focal Reaction. While in the 

 preceding pages the attention has been centered on the fact that 

 a variety of agents may be used to elicit the tuberculin reac- 



* The so-called sensitization of the skin to metallic colloids is similar in 

 character. Hift found, for instance, that if he injected electrargol intravenously 

 after having injected small amounts into the skin previously, the involuted skin 

 papules would again flare up. 



