208 ACTIVE IMMUNIZATION 



which every injection is followed by a reaction which is evidently 

 detrimental to the patient. 



In our account of anaphylaxis we have already drawn attention 

 to this occurrence and have studied the mechanism which underlies 

 its production. I would merely emphasize at this place that in 

 tuberculosis, probably more than in any other of the infectious 

 diseases, anaphylactic processes are responsible for many of the 

 phenomena which go to make up the clinical picture of the disease. 

 In the days when Koch's early work on tuberculin was done, nothing 

 was as yet known of anaphylaxis, and the symptoms following its 

 injection were generally attributed to associated toxic substances. 

 Koch hence directed his efforts to the preparation of a less toxic 

 product, especially as he had not succeeded in producing an 

 actual immunity in his experimental animals with the old tuber- 

 culin. 



As it was out of the question to use killed-off cultures as such, 

 owing to the production of abscesses when used hypodermically, or 

 the formation of nodules in the lungs when injected intravenously, 

 Koch resorted to the following procedure : Young cultures which had 

 been dried in the vacuum were ground to pieces in a specially 

 constructed apparatus, and the resultant powder shaken with 

 distilled water, and then centrifugalized. The residue constitutes 

 Koch's so-called T. R. preparation, while the supernatant fluid was 

 termed T. O. Subsequently he brought out his New (neu) Tuber- 

 culin, which is practically an aqueous emulsion of the entire organ- 

 isms, pulverized to mere fragments, and preserved by the addition 

 of 50 per cent, of glycerin. 



Although the use of the old tuberculin is still continued, this new 

 product is rapidly gaining in favor and virtually corresponds to the 

 bacterial vaccines which we have considered heretofore. Its anti- 

 genie power is proved by the fact that on treatment with this material 

 the agglutinin titer of the patient's serum is frequently raised as 

 high as 1 : 500. This, to be sure, does not constitute an index to the 

 degree of immunity which is produced, but it proves that the sub- 

 stance in question has the power to bring about that general allergic 

 state of which agglutinin production is one of the possible 

 manifestations. 



Dosage and Injection. Old Tuberculin. The old tuberculin is put 

 up in 1 c.c. and 5 c.c. ampules. Unless a very large number of 



