VARIOUS TUBERCULIN PREPARATIONS 63 



turbid fluid is centrifugalized. The sediment thus obtained composes the T. R. or 

 the tubercle bacilli residue. 



T. R. therefore contains the aqueous insoluble components of the tubercle bacillus, 

 while the soluble ones are retained in the opalescent supernatant fluid which Koch 

 calls TO (Tuberculin Original). 



T. R. is readily assimilated by patients. If carefully administered it produces very 

 little infiltration and only slight temperature and general reaction. Its price is com- 

 paratively high (i c.cm. costs 8.50 marks). 



The first preparation which contained both the soluble and insoluble 

 elements of the living bacilli was the 



/. New Tuberculin Bacilli emulsion (B. E.) which consists of T. R.+ 

 T. O. 



The living tubercle bacilli are first pulverized in a mortar and then suspended 

 in salt solution. Centrifugalization is not necessary, but sedimentation is required; 

 50 per cent, glycerin is added for preservation purposes. Next to T. the new 

 tuberculin B. E. has been most carefully studied. 



B. E. also lacks in being an ideal antigen inasmuch as immunity attained by 

 its injections is not at all proof against subsequent infection. 



Closely resembling the B. E. is 

 g. The Tuberculin of Beraneck. 



Beraneck produced two tuberculin preparations of which one is in the main identical 

 with TOA, while the other is an extract of tubercle bacilli with i per cent, of phosphoric 

 acid. These tuberculins are mixed and applied together. Sahli reports good results 

 with this mixture. 



Although none of the described tuberculin preparations can 



Action of be considered a true antigen of the tubercle bacillus, they 



Tuberculin, undoubtedly have a favorable effect upon tuberculous 



individuals. To a certain extent the benefits are derived by 



the mechanism of partial immunization. This in itself does not, however, 



explain the entire phenomenon of their successful action. 



On examination of the tuberculous organs of animals treated with 

 tuberculin, there will be found within the healthy tissue surrounding the 

 tuberculous foci, a fresh inflammatory reaction. This consists of a sero- 

 fibrinous exudate and a zone of leucocytes intruding to a certain extent 

 upon the tubercular lesion. Tuberculin acts only upon tuberculous tissue 

 which is still alive and not upon dead, cheesy or necrotic structures. 



If enough tuberculin is given so that death of a tuberculous guinea-pig occurs, 

 the changes found are striking. On dissection, about the point of inoculation Koch 

 reports a marked congestion of the blood vessels giving a red and often an almost dark 

 violet appearance. This discoloration extends for a greater or less distance from the 



