IMMUNITY PHENOMENA IN TUBERCULOSIS 293 



is there. He gives a record of 280 cases where the value of the method 

 was tested by subsequent post-mortem examination. He found that with 

 proper precautions the error was only 3 "3 per cent. The method has 

 been largely practised in all parts of the world, and is of great value. 



(2) Immunity Phenomena in Tuberculosis. — Although 

 recovery from tuberculosis is of frequent occurrence in man, we 

 have at present no clear idea of the processes at work. The 

 object of the therapeutic application of the tuberculins introduced 

 by Koch was to increase the hypothetically existing powers of 

 resistance of the infected individual. The underlying principle 

 was thus the same as in immunisation procedures (e.g., against 

 the typhoid bacillus) with the difference that immunisation was 

 proceeding in an already infected x animal. One result has 

 been to stimulate inquiries with a view to observing whether 

 the sera of persons suffering from tuberculosis possess the 

 qualities associated with immunity reactions. 



(1) Immune-bodies and Precipitins. — Evidence for the exist- 

 ence of the former in tuberculosis has been sought by applying 

 the method of complement fixation (see p. 127), e.g., the serum 

 of a tubercular animal being mixed with tuberculin, the mixture 

 is tested for its capacity of absorbing complement. Following 

 this line, Wassermann and others have found evidence of the 

 presence of an antitubereulin in tubercular foci. Generally speak- 

 ing, such an antitubereulin is absent from the blood serum of 

 most tubercular patients. In certain cases it may be present in 

 the serum of patients subjected to repeated tuberculin injections. 

 Another immunity phenomenon which may be observed is the 

 formation of a precipitate when some of the serum of a tuber- 

 culous patient is added to a solution of tuberculin, the mixture 

 being allowed to stand for twenty-four hours (precipitin reaction). 

 There is thus evidence in some tubercular infections of a vital 

 reaction resulting in the formation of antagonistic bodies, which 

 may include both immune-bodies and precipitins. It may be 

 said, however, that the sera of certain animals, e.g., rabbit and 

 ox, when mixed with tuberculin, become capable of deviating 

 complement from a haemolytic combination. 



(2) Agglutinins. — The serum of tubercular patients has been 

 found to exert an agglutinating action on the tubercle bacillus. 

 A convenient method is to add different amounts of serum, com- 

 mencing with, say, 1 c.c, to quantities of a dilution of the new 

 tuberculin (Bazillenemulsion) equivalent to 1 part of the 

 bacterial bodies to 10,000 of diluent, and to leave the mixture 

 for twenty-four hours before observing. As with other agglutin- 

 ative observations, it is difficult to correlate the degree of 



