ACTIVE IMMUNISATION AGAINST TUBERCLE. 237 



It differs from tuberculin O, and also from tuberculin as 

 originally made, in that it contains the substances present 

 in the bacilli, which are insoluble in glycerine. Tuberculin O 

 produces the tuberculin reaction like the original glycerine 

 extract, but tuberculin R only does so in large doses. The 

 most important difference, however, is that the latter when 

 injected into animals in repeated doses, produces im- 

 munity against the original extract, against tuberculin O, 

 and against living and virulent tubercle bacilli. As supplied 

 commercially, each c.c. corresponds to 10 mgrms. of dried 

 bacilli. Immunisation is carried out by hypodermic injec- 

 tion, commencing with doses of -^ mgrm. of the latter, 

 the necessary dilutions being made with . 7 5 per cent sodium 

 chloride solution. The injections are practised every second 

 day till a dose of 20 mgrms. can be tolerated. In this way, 

 Koch succeeded in immunising a number of guinea-pigs 

 so that the injection of virulent tubercle bacilli had no 

 effect. In other cases the disease produced by the latter 

 was much more localised than is usually the case. He also 

 treated guinea-pigs already infected. For the cure of these 

 the treatment had to be commenced within a fortnight of 

 inoculation. In more advanced cases there was a tendency 

 to improvement in the tubercular lesions. In the case of 

 man, it is early cases of tuberculosis which are likely to be 

 most benefited. The cases of phthisis to be treated should 

 be those in which the temperature does not rise above 

 100.5 F., and no dose must be given which raises the 

 temperature more than half a degree. In such cases, as 

 also in lupus, improvement has been observed, the tempera- 

 ture becoming lower and the weight increased. Unlike 

 ordinary tuberculin, there is with this " residual " tuberculin 

 no local reaction when it is administered as above, and no 

 general bad effects have followed its use. Much further 

 work must of course be done before we can judge of the 

 value of this new departure. The principle involved is the 

 production by means of the intracellular poisons of the 

 tubercle bacillus of an active immunity in the bo 

 animal already invaded by the bacillus. - 



