TUBERCULOSIS 129 



has not fulfilled -what was expected of it, has at any rate 

 been the means of bringing to notice the possibility of 

 combating disease by injecting into the patient toxins 

 ready-made which are liberated in the ordinary course of 

 disease, and has led the way to the investigation of anti- 

 toxin treatments in diphtheria, cholera, etc. 



It has also been found of use in the diagnosis of tubercle, 

 and in the treatment of lupus. If, however, it be injected 

 into a patient in whom phthisis is dormant, it is very apt 

 to cause the old trouble to break out afresh. 



In the diagnosis of tuberculosis in cattle it is very valu- 

 able, the percentage of failures being less than 1 per cent. 



Preparation of Kocli's Tuberculin. — This is a liquid con- 

 taining in a concentrated form the metabolic products of 

 the growth of the tubercle bacillus. He grows the tubercle 

 bacillus in glycerine-peptone-broth in flat-bottomed flasks 

 for six or eight weeks at blood-heat. A thick white skin is 

 formed, which first floats on the surface, but afterwards 

 sinks to the bottom. The cultures are subsequently ex- 

 amined microscopically for impurities, and then gently 

 evaporated on a water-bath to about an eighth of their 

 bulk, then filtered through a Pasteur-Chamberland filter. 

 In this way he obtains the metabolic products of the 

 organism alone, without their intracellular contents. The 

 concentrated liquid so produced contains 40 to 50 per cent, 

 of glycerine, and the presence of the glycerine prevents 

 'the growth of any saprophytic organisms that may acciden- 

 tally gain access to it. From this liquid the tuberculin 

 may be precipitated by the addition of absolute alcohol. 



Practical Disinfection. — The sputa should be received into 

 5 per cent, carbolic or mercuric chloride, and never per- 

 mitted to dry on handkerchiefs. Phthisical patients should 

 not expectorate in the streets, but should carry a proper 

 receiver with them to receive the sputum. Where a vessel 



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