CHAPTER IV 

 THE FOCAL REACTION 



In the preceding chapter the changes that take place in the 

 organism after nonspecific injections have been discussed in detail. 

 We will now have to consider a related subject of utmost importance 

 from the therapeutic as well as the theoretical standpoint, namely, the 

 focal reaction that becomes evident about inflammatory foci after 

 nonspecific injections. Just as the general symptomatology of the 

 patient may be accentuated after the injections, so it has been ob- 

 served that preexisting inflammatory lesions, endogenous or exogenous 

 in origin, will very frequently become more acute, with an apparent 

 increase in pain, tenderness and hyperemia. This increased reaction 

 is usually followed by a diminution of the objective evidences of 

 inflammation until in many instances a complete restitution to the 

 normal is brought about. In order to understand the possible sig- 

 nificance and therapeutic importance of this phenomenon it will be 

 necessary to briefly review our present conception of such focal re- 

 actions. 



Ever since the tuberculins were introduced early in the nineties 

 the concept of the focal reaction, the "Herd Reaktion," at the site 

 of the inflammatory lesion has been so closely associated with the 

 diagnostic and the therapeutic principles of the tuberculin as hypothe- 

 cated by Koch that the field has been limited largely to a con- 

 sideration of this particular disease. This view of the focal reaction, 

 exemplified, let us say, in a local disease such as lupus or an apical 

 involvement, needs no further elucidation. By some the term "local 

 reaction" is, however, used synonymously; it should of course be 

 reversed for those reactions that occur at the site of the injection 

 of the tuberculins. 



By common consent we may assume that positive local and gen- 

 eral reactions are regarded as corroborative evidence that at some 

 time the organism has been infected with tubercle bacilli; to the 

 focal reaction we generally attach greater significance in so far that 

 the observation of the focal reaction following tuberculin injection 

 is regarded as proof not only of infection but of activity as well. It 

 is regarded as strictly specific in the sense that only tuberculous 

 processes respond to tuberculin injections. On this assumption the 



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