446 THE TUBERCLE BACILLUS GROUP 



solution and suspension. This constitutes new tuberculin. The new 

 tuberculin is finally prepared of such a strength that 1 c.c. of the 

 dried residue will contain 0.002 gram of solid material. It is cus- 

 tomary to add glycerin 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 sub- 

 stances 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 c.c. of the solution 

 contains the equivalent of 0.001 gram of dried tubercle bacilli. It 

 will be seen that the bacillus emulsion contains both new tuber- 

 culin and a certain amount of the water-soluble products of the 

 tubercle bacillus or old tuberculin. 



Alkaline Tuberculin (T. A.). Virulent 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 filtered. The clear 

 fluid (T. O.) gives similar but somewhat more severe reactions than 

 the regular tuberculin. It often leads to sterile abscess formation. 1 



DIAGNOSIS OF TUBERCULOSIS. 



A. Clinical, by tuberculin reaction. 



1. Action of tuberculin on healthy animals and man. 



2. Action of tuberculin on tuberculous animals and man. 



3. Principle of tuberculin reaction. 



1 For a general survey of the nature and composition of various tuberculins see Kuthy 

 and Wolff-Eisner, Die Prognosenstellung bei der Lungentuberkulose, Berlin and Vienna. 

 1914, pp. 438-446. " 



