KOCH'S NEW TUBERCULIN. 263 



The method is applied as follows. The animals are kept twenty- 

 four hours in their byres and the temperature is taken every 

 three hours, from four hours before the injection till twenty -four 

 after. The average temperature in cattle is 102.2° F. ; 30 to 

 40 centigrammes of tuberculin are injected, and if the animal 

 be tubercular the temperature rises 2° or 3° F. in eight to twelve 

 hours and continues elevated for ten to twelve hours. Bang, 

 who has worked most at the subject, lays down the principle 

 that the more nearly the temperature approaches 104° F. the 

 more reason for suspicion is there. He gives a record of 280 

 cases where the value of the method was tested by subse- 

 quent post-mortem examination. He found that with proper 

 precautions the error was only 3.3 per cent. The method is 

 largely practised on the Continent, and ought to be more widely 

 applied, 



Koch's New Tuberculin. — Koch in 1897 published the 

 results of further researches on tuberculosis. These consisted 

 (i) of an attempt to immunise animals against the tubercle 

 bacillus by employing its intracellular toxins ; (2) of trying to 

 utilise such an immunisation to aid the tissues of an animal 

 already attacked with tubercle the better to combat the effects 

 of the bacilli. The method of obtaining the intracellular 

 toxins was as follows. Bacilli from young virulent cultures 

 were dried in vacuo, and disintegrated with an agate pestle and 

 mortar, treated with distilled water and centrifugalised. The 

 clear fluid was decanted, and is called by Koch " tuberculin O." 

 It has the properties of the ordinary tuberculin. The remain- 

 ing deposit was again dried, bruised, treated with water and 

 centrifugalised, the clear fluid being again decanted, and this 

 process was repeated with successive residues till no residue 

 remained. These fluids put together constitute what Koch 

 calls "tuberculin R." It is said to contain the substances 

 present in the bacilli, which are insoluble in glycerin and only 

 produce a tuberculin reaction in large doses. When injected 

 into animals in repeated and increasing doses, -^^ mgrm. being 

 the initial dose, it is said to produce immunity against the 

 original extract, against " tuberculin O," and against living and 

 virulent tubercle bacilli; but regarding this, opinions differ. 

 Cases of early phthisis in man and of lupus have been treated 

 with " tuberculin R," no dose being given which raises the 



