352 THE BACILLUS OF TUBERCULOSIS 



In order safely to kill all tubercle bacilli contained in tubercular 

 sputum it is necessary to boil it for five minutes at 100 C. The 

 bacilli are very resistant to dry heat and can withstand 100 C. for 

 one hour. Corrosive sublimate cannot be safely used to disinfect 

 sputum, pus, caseous material, etc., because a peripheral coagulation 

 of the albumen prevents its penetration into the interior of the masses 

 containing the bacilli. Carbolic acid (5 per cent.) added to tubercular 

 material in liberal quantities kills the organism within a few hours. 

 Formalin is not trustworthy as a disinfectant for tubercular albumin- 

 ous material. 



Tubercle Bacilli in the Circulating Blood. In much advanced cases 

 tubercle bacilli have occasionally been found in the circulating 

 blood, but this is an exceptional occurrence. They evidently do not 

 multiply in the blood and are filtered out very soon after entering it. 

 It therefore occasioned considerable surprise when Rosenberger 

 claimed that he had been able to show that tubercle bacilli are present 

 in the blood even in the most incipient cases. In other words, 

 Rosenberger claimed that tuberculosis was a bacteriemia. However, it 

 has been shown by McFarland and his co-workers, and by Ravenel 

 and Smith, that this statement is incorrect for human tuberculosis. 

 Schroeder, Col ton, and Mohler examined the blood of 50 tubercular 

 cows, not merely by staining methods, but by the inoculation of 135 

 guinea-pigs, and found that Rosenberger's claim was entirely un- 

 substantiated; tuberculosis accordingly is a bacteriemia neither in 

 man nor cattle. Rosenberger in his painstaking work became the 

 victim of a deceptive acid-fast bacillus often found in distilled water 

 used in laboratories. 



TUBERCULIN TESTS THE DIAGNOSIS OF LATENT TUBER- 

 CULOSIS IN CATTLE. 



Koch's Old Tuberculin. Koch's old tuberculin, also known as 

 Tuberculin Original, or Koch's O. T., is prepared as follows: A 

 veal bouillon, containing 3 to 5 per cent, glycerin and the usual 

 amounts of common salt (J per cent.) and pepton (1 per cent.), 

 having been made slightly alkaline and kept in a flask, is inoculated 

 on the surface from a pure culture of tubercle bacilli. The flask is 

 then kept in the incubator at blood temperature from three to six 

 weeks. During this time a thick, dry, crumpled, whitish layer forms 

 on the surface. When this is well developed stains are prepared 

 from it, and if the culture is found to be pure and uncontaminated 

 it is evaporated on a water bath at a temperature of 70 to 80 C. 

 down to one-tenth of its original bulk. The thick brown liquid so 

 obtained, containing from 30 to 50 per cent, glycerin, is first filtered 

 through chemical filter paper and then through a Chamberland or 

 Pasteur filter. The product of these manipulations is known as 



