Tuberculin Ruckstand (Residue)—T. R. Announced by Koch in 1897.
Ground, dried tubercle bacilli.
Distilled water added.
Centrifugalization.
Supernatant fluid removed (not to be used).
Sediment dried and ground; distilled water added; centrifugalization.
Fluid removed and set aside.
Sediment dried and ground again; distilled water added; centrifugalization.
Fluid removed and set aside.
Sediment dried and ground, etc., as above.