IMMTXITV I'HKXOMKXA IX TriJKIK'ULO-TS -JSO 



the method of complement fixation (see p. 130), e.y. the serum 

 of a tubercular animal being mixed with tuberculin, the mixture 

 is tested for its capacity of absorbing complement. Following 

 this line, Wasserman and others have found evidence of the 

 presence of an antituberculin in tubercular foci, and this is 

 taken as an indication of the occurrence of a vital reaction 

 against the poisons of an invading organism. Generally speak- 

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

 most tubercular patients. It is present, however, in the serum 

 of such individuals after they have been subjected to repeated 

 tuberculin injections. Here it is chiefly seen when a patient is 

 losing the capacity for reacting to the injections. Another 

 immunity phenomenon which may be observed is the formation 

 of a precipitate when some of the serum of a tuberculous patient 

 is added to a solution of tuberculin, the mixture being allowed 

 to stand for twenty-four hours (precipitin reaction). The exact 

 relationship of such precipitins to immune-bodies is still doubtful ; 

 that it is a close one is shown by the fact that such precipitates 

 have the property of absorbing complement. At present it is 

 enough to say that there is evidence in tubercular infection of a 

 vital reaction resulting in the formation of antagonistic bodies, 

 which may include both immune-bodies and precipitins. In sup- 

 port of the view that immune-bodies exist against the tubercle 

 bacillus, it may be said 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 (Bazillenemuhion) equivalent to 1 part of the 

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

 twenty-four hours before observing. As with other agglutinative 

 observations, it is difficult to correlate the degree of agglutinating 

 power of the serum with the degree of immunisation possessed 

 1 > v the individual from which it was derived. The method has 

 been used by some as a means of diagnosis, but its value is 

 doubtful and is certainly inferior to the methods depending on 

 supersensitivcness. 



(3) Opsonins. The serum of most normal men and of several 

 s|n'cies of animals normally contains opsonins to the tubercle 

 bacillus. The opsonic effect is also manifested in varying 

 degree by the serum during the course of natural infection ; 

 such variations are considered l>elow. 



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