TUBERCLE BACILLUS 483 
up dried tubercle bacilli in ball mills to an impalpable powder, and to 
suspend or partially dissolve this powder in salt solution with or 
without the addition of glycerin. 
New Tuberculin (T. R. Koch).'— Young virulent tubercle bacilli are 
dried first between sheets of sterile filter paper, then in vacuo over 
sulphuric acid and phosphorus pentoxide until thoroughly anhydrous, 
then ground in a mortar until a dry powder is obtained. This powder 
is suspended in water, thoroughly mixed, and then centrifugalized. 
The first supernatant fluid obtained (T. O.) is rejected. This pre- 
liminary grinding with water is intended to wash out the water-soluble 
substance. The residue is then repeatedly ground and centrifugalized, 
saving the supernatant liquid each time until all of it has passed into 
solution and suspension. This constitutes new tuberculin. The new 
tuberculin is finally prepared of such a strength that 1 cc. of the 
dried residue will contain 0.002 gm. of solid material. It is cus- 
tomary to add gl\cerin and a small amount of formaldehyde to the 
preparation before it is finally made up to strength. 
At times new tuberculin has been found to contain living, virulent 
tubercle bacilli, although they are killed by prolonged exposure to 
formalin. New tuberculin was originally intended for curative pur- 
poses, as it was found to be relatively free from the toxic substances 
which are found in old tuberculin. The theoretical inherent dangers 
of this preparation, however, have tended in the past to limit its use. 
Bacillus Emulsion (B. E.).^— This is an emulsion of untreated tubercle 
bacilli which are washed and dried as for new tuberculin. The organ- 
isms are ground thoroughly and then suspended by continual grinding 
in physiological salt solution containing about 20 per cent of glycerin. 
From 0.25 to 0.5 per cent carbolic acid is added to kill whatever 
tubercle bacilli or other organisms may have been included in the 
preparation. For use it is standardized so that 1 cc. of the solution 
contains the equivalent of 0.001 gm. of dried tubercle bacilli. It will 
be seen that the bacillus emulsion contains both new tuberculin and 
a certain amount of the water-soluble products of the tubercle bacillus 
or old tuberculin. 
Alkaline Tuberculin (T. A.). — Mrulent tubercle bacilli freed from 
culture media are extracted with 10 per cent caustic soda for three to 
four days at 20° C. The bacilli and their fragments are then removed 
by filtration through filter paper. The filtrate is neutralized by the 
careful addition of hydrochloric acid and again fihered. The clear 
fluid (T. A.) gives similar but somewhat more severe reactions than 
the regular tuberculin. It often leads to sterile abscess formation.^ 
1 Deutsch. med. Wchnschr., 1897, 23, 209. 
2 Koeh: Deutsch. med. Wchnschr., 1901, No. 3. 
' For a general survey of the nature and composition of various tuberculins see 
Kuthy and Wolff -Eisner (Die Prognosenstellung bei der Lungentubprkulose, Berlin and 
Vienna, 1914, pp. 4.38-446). See also Calmette: Loc. cit., p. 71 cl se^. 
