148 THE METHOD OF COMPLEMENT FIXATION. 



easily. Finally the antituberculin receptors become so numerous that they 

 are detached from the cells and become free receptors. This period, however, 

 is only transitory, as is corroborated by the difficulty connected with the 

 demonstration of these antibodies in the focus. This free antituberculin 

 combines with the tuberculin (spontaneously formed or injected) and attracts 

 the complement, or the complement producing phagocytes. Uncombined 

 complement has no effect on the tissues. It is different, however, with the 

 phagocytes. These can without any additional help act directly upon the 

 infected focus. If the tuberculin treatment is continued, a period arises 

 during which the antituberculin bodies are so greatly accumulated in the 

 local focus that they ultimately escape into the blood stream. This freely 

 circulating antituberculin neutralizes any freshly injected tuberculin, so 

 that such patients become refractory even against the largest amounts of it. 

 (Tuberculin immunity.) Tuberculin immunity is not, however, in all cases 

 to be identified with a strong antituberculin content in the serum. For 

 example, it is very difficult to stimulate antituberculin by treatment with 

 S. B. E., although by its use an immunity against B. E. is easily attained. 



In former times a negative tuberculin reaction after a prolonged treatment was 

 stamped as a cure of the tuberculosis, a fact obviously incorrect; for, no matter how 

 successful the tuberculin therapy may be, it cannot be considered as a complete curative 

 procedure. 



The appearance of antituberculin in the general circulation is interpreted in a double 

 light. Wassermann and Bruck advised that it was best to avoid its appearance, because 

 by its presence here the tuberculin is neutralized without ever reaching the focus where 

 it is required. On the other hand, it may be considered a protective element in that it 

 binds any tuberculin which may spontaneously be formed in the system. In general, 

 that method should be adopted which makes the subject non-susceptible to the largest doses of 

 tuberculin. In practice it was found that those patients having the greatest amounts of 

 antituberculin in their serum, generally offered a better prognosis than the others. 



Recent experiments of the author seemed to show that in certain cases serum con- 

 taining antituberculin can raise the susceptibility for tuberculin. Thus tuberculous 

 guinea-pigs injected with a mixture of tuberculin, antituberculin and complement in pro- 

 portionate dosage, died in several hours, while animals of the same kind receiving only 

 tuberculin or tuberculin + antituberculin remained alive. 



i The experiences gained by the employment of the complement 



Serum fixation test in tuberculosis, lead to its application in the study 



Diagnosis of of syphilis. The difficulties in this disease were greater, inas- 



Syphilis. much as there were no bacteria or preparations like tuberculin 



which could be used as antigen. 



Syphilitic organ extracts were employed instead, with the idea that these would 

 contain the specific virus. The serum of monkeys previously immunized with such 

 extracts when mixed in vitro with the latter, gave complement fixation. This experi- 

 ment is not, however, conclusive as the positive reaction may be due to anti-human 

 proteid amboceptors produced at the same time by the injection of the human serum 

 contained in the organ extract. The experiment was changed and the syphilitic organ 



