The process continued until water takes up the sediment, then all the fluids set aside (except the first one) mixed together.
Glycerine 20% added.
The mixture is T. R.
Koch was prompted by the following consideration in bringing out T. R.: He thought that the Old Tuberculin conferred only a toxic immunity, not bacterial. T. R. was supposed to confer bacterial immunity.
Each 1 cc. of T. R. contains 10 milligrams of dried bacilli.
Bacillen Emulsion—B. E. Announced by Koch in 1901.
Finely powdered tubercle bacilli—1⁄2 gram.
50 cc. of water and 50 cc. of glycerine.
All mixed together—prolonged shaking.
B. E. is supposed to contain not only the extract of the body of the tubercle bacilli, as in T. R., but also its soluble products (which in the case of T. R. were discarded in setting aside the supernatant fluid).