302 A MANUAL OF BACTERIOLOGY 



this view. Spores are usually single and not multiple, 

 and are regular spherical or ovoid bodies, whereas the 

 unstained spaces in the tubercle rods are irregular. More- 

 over, in the same specimen of sputum a varying amount 

 of " beading," as it is termed, may be brought out by 

 different staining methods (Plate VIII. 6) ; 'in a prepara- 

 tion stained by Gram's method it is usually more pro- 

 nounced than in one stained with carbol-fuchsin. In class 

 work also it will be found that one student's specimen will 

 show beading much more markedly than another's. These 

 considerations render it probable that the beading is partly 

 due to segmentation of the protoplasm, and partly, perhaps, 

 is an artifact due to the staining process, and is not a 

 spore formation. The tubercle bacillus, however, probably 

 does 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, filamentous 

 forms develop, and Foulerton 1 and others include it 

 among the Streptotrichece. The bacillus is agglutinated 

 by the blood-serum of a tuberculous animal (see p. 324). 

 There are several varieties of the tubercle bacillus (see 

 pp. 315 and 319). 



Staining reactions. The tubercle bacillus stains in- 

 differently 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 

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



