CHAPTER VII • 



VACCINES : DIAGNOSTIC AND CURATIVE 



The premature announcement in Germany, in 1891, of 

 the discovery by Koch of tuberculin and its curative 

 properties was followed by the administration of ex- 

 cessive doses. This caused a temporary discredit to 

 fall on the use of the reagent as a curative vaccine for 

 phthisis in man, and to the present day opinion is still 

 divided on this subject. But as a diagnostic reagent 

 for cattle, tuberculin, in competent hands, has proved 

 of the greatest value in eradicating tuberculosis from 

 affected herds, and in preventing its reintroduction by 

 newly-bought animals. Probably it was the success 

 claimed for tuberculin which led the Russians, Kalning 

 and Helman, to prepare mallein on the same lines. 

 Independently of the reduction of the equine popula- 

 tion owing to mechanical traction, the proportion of 

 horses affected with glanders in Great Britain has 

 been enormously reduced, and Hunting's work on this 

 disease in London has probably been the means of 

 preventing the infection of many men whose work 

 brings them in contact with large numbers of horses. 



The tuberculin test as applied to cattle is now familiar 

 to all intelligent stock-owners. The preparation of 

 the reagent varies in small details in different labora- 

 tories, but, broadly speaking, a glycerine-broth culture 

 of the tubercle bacillus is killed by heat, filtered to 



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