Chemistry 675 



respond to the virulence of the culture; that doses of i mg. of a 

 very virulent culture may induce general tuberculosis in rabbits 

 in a very short time; that 20 mg. of a bacillus of low virulence may 

 fail to produce any lesion in rabbits or guinea-pigs; that no mor- 

 phologic relationship could be observed between the bacilli and their 

 virulence; that highly virulent bacilli 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 

 virulence; 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 

 tuberculosis 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 trans- 

 missions in other than human hosts. 



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 42C., can be extracted with ether. 

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

 The other is insoluble in ether, t>ut soluble in benzole, with which 

 it can be extracted. It melts at about 5oC. 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 Schweinitzf showed that it was possible to extract from 

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

 teraconic acid. It melts at 161 to i64C. and is soluble in ether, 

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

 organism depend upon it. 



RuppelJ believes that three different fatty substances are present 

 in the tubercle bacillus, making up from 8 to 26 per cent, by weight. 

 The first can be extracted with cold alcohol, the second with hot 

 alcohol, the third with ether. In addition to the fatty substance 

 Ruppel also found what he believes to be a protamin, and calls 

 tuber culosamin. It seems to be combined with nucleinic acid, and, 

 indeed, from it he isolated an acid for which he proposes the name 

 tuberculinic acid. 



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



t "Trans. Assoc. of Amer. Phys.," 1897; "Centralbl. f. Bakt.," etc., Sept. 15, 

 1897, Bd. xxn, p. 200. 



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



