THE TUBERCLE BACILLUS 369 



process, and is not a spore formation. The tubercle 

 bacillus may, however, form spores, though this is a 

 debated point. Some observers have described clear, 

 regular, unstained spaces in bacilli from old cultivations, 

 and consider these to be true spores. 



The tubercle bacillus is a non-motile, strictly parasitic 

 organism (it has been described as being both motile and 

 flagellated). It usually occurs singly, occasionally linked 

 in twos or threes so as to form short chains, and under 

 certain conditions, especially in old cultures, branched 

 filaments develop, so that Foulerton l and others 

 include it among the filamentous forms. The bacillus 

 is agglutinated by the blood-serum of a tuberculous 

 individual or animal. There are several varieties of the 

 tubercle bacillus (see pp. 379 and 380), but the general 

 morphological, staining, and cultural characters are much 

 the same for all. 



Staining reactions. The tubercle bacillus from whatever 

 source stains indifferently with the ordinary watery 

 solutions of dyes, prolonged treatment with, or warming, 

 the solution being required. It stains well by Gram's 

 method. It also stains well and deeply with carbol- 

 fuchsin, particularly on warming, and when so stained is 

 markedly resistant to the decolorising action of 25-30 

 per cent, mineral acid ; that is to say, it is strongly 

 11 acid-fast," and this property is made use of for demon- 

 strating its presence in tissues, etc., and for diagnostic 

 purposes. This " acid-fastness " is due to the chemical 

 constitution of the bacillus (see p. 375). Some of the 

 bacilli in the lesions, particularly when old or healing, 

 probably do not stain, and red-staining granules may 

 more or less take the place of definite bacilli : these are 

 the " splitter " forms of Spengler. 



Cultural characters. The tubercle bacillus is aerobic 



1 " Milroy Lectures," Lancet, 1910, vol. i, pp. 551 et seq. 

 M.B. 24 



