356 LOCAL TISSUE REACTIVITY 



When tuberculin is suhsecjucntly introduced into the circula- 

 tion, the site ol local c uianeous or conjunctival tid)erculin reac- 

 tion frecjuently shows a new inflammatory process (Klinomiiller, 

 1903, and Siatincl-ano, 1907) . The "flare-tip" ("anflannnung") 

 may also be produced by intracutaneous injection of tuberculin 

 in the \icinity of the site of a previous tuberculin test. V. Pirquet 

 noted a prooressive increase in intensity of reacticjn with con- 

 secutive cutaneous reactions at fresh sites. Weiss (1925) obtained 

 reactions which developed at an increased rate on repetition of 

 the V. Pirc[uet test at the same site. 



W^illis (1925-26) inoculated guinea pigs with an avirulent strain 

 R-L T^vo years after injection these animals no longer gave a 

 definite skin reaction, but on reinocidation with a virulent strain, 

 sensitivity redeveloped so rapidly that necrotic reactions were ob- 

 tained four days later, when the normal animals receiving the 

 same virulent dose ^vere still negative. 



Parenteral injections of tid)ercidin in sensitive animals and 

 man in sufficiently large amoinits produce a decrease or abolition 

 of sensitivity so that the second test may yield negative results 

 within a few days. The generally accepted opinion is that the 

 process is one of desensitization rather than of immunity since 

 the tolerance may rapidly disappear on cessation of treatment. 

 It is of special interest that there is no evidence of any degree 

 of immunity against the toxic action of tid:)erculin in the allergic 

 subjec t. 



Certain microorganisms (Streptococcus virldaiis and pneumo- 

 coccus) have the capacity to produce secondary reactions de- 

 scribed by Swih and his associates (1926) . When the microorgan- 

 isms are injected intradermally in rabbits there is a slight redness 

 and swelling Avhich subsides ^vithin two or three days. About a 

 week later a seconclary reaction appears in the site of the original 

 injection. It consists of redness and s^velling and may have out- 

 lined red satellites ^vhich sometimes fuse with the main lesion. 

 The reaction takes one to three days. The investigations of 

 Derick and Andrewes (1926) point to the close similarity be- 

 tween this secondary reaction and tid^erculin hypersensitiveness. 



The first experiments ^\hich demonstrated skin hypersensitive- 

 ness lollo\ving the injection of dead organisms ^vere published by 

 Gay and Force (1914) • The tests were made with typhoidin, an 



