7i8 Tuberculosis 



phologic relationship could be observed between the bacilli and their 

 virulence; that highly virulent bacilH grew scantily on culture- 

 media and were short lived; that bacilli of widely different virulence 

 may be present in any one of the various human tuberculous lesions; 

 that in scrofulous lymphadenitis the bacilli are usually of low viru- 

 lence; the bacilli in pulmonary tuberculosis with ulceration are 

 of feeble virulence, those of miliary tuberculosis of very great viru- 

 lence; that the so-called "healed tubercles" of the lung may con- 

 tain virulent or attenuated bacilli; that individuals suffering from 

 infection with a bacillus of a low grade of virulence may be again 

 infected with extremely virulent tubercle bacilli; that chronic tub- 

 erculosis of the bones may contain bacilli of high or low virulence, 

 and that variations in virulence among human tubercle bacilli 

 may possibly sometimes depend, like many other qualities among 

 tubercle bacilli, on peculiarities inherited through serial transmis- 

 sions in other than human hosts. 



Metabolism. — Tubercle bacilli require a plentiful supply of oxygen 

 and therefore grow only upon the surface of culture-media. They 

 produce no diastatic enzyme and give off no gas from cultures con- 

 taining carbohydrates . Carrier * and Wells and Cooper f have shown 

 that they produce some lipase, and Kendall, Walker, and DayJ that 

 they produce some esterase. 



They disintegrate protein with the production of amino-acids and 

 ammonia. In doing so no indol is formed. They do not produce 

 enzymes by which gelatin is softened, blood-serum digested or 

 milk coagulated or digested. 



Chemistry of the Tubercle Bacillus. — Klebs§ found that the 

 tubercle bacillus contains two fatty bodies, one of which, having a 

 reddish color and melting at 42°C., can be extracted with ether. 

 It forms about 20 per cent, by weight of the bacillary substance. 

 The other is insoluble in ether, but soluble in benzole, with which 

 it can be extracted. It melts at about so°C. and constitutes 1.14 

 per cent, of the bacillary substance. After removing these fatty 

 bodies the bacilli fail to resist the decolorant action of acids when 

 stained by ordinary methods, so that it seems probable that their 

 acid-resisting power depends upon them. 



De Schweinitz|| showed that it was possible to extract from 

 the tubercle bacillus an acid closely resembling, if not identical with, ■ 

 teraconic acid. It melted at 161° to i64°C. and was soluble in ether, 

 water, and alcohol. He thought the necrotic changes caused by the 

 organism depended upon it., 



Ruppel** believed that three different fatty substances were present 



* " Compt. -rendu de la Soc. de Biol, de Paris," 1901, uii, 320. 

 t Jour. Infectious Diseases, 1912, xi, 388. 

 + "Jour. Infectious Diseases," 1914, xv, 443. 

 § " Centralbl. f. Bakt.," 1896, xx, p. 488. 



II "Trans. Assoc, of Amer. Phys.," 1897; "Centralbl. i. Bakt.," etc., Sept. 15. 

 1897, Bd. XXII, p. 200. 



** "Zeitschrift fur physiol. Chemie," 1899, xxvi. 



