TUBERCULOSIS. 295 



made to stain like the spores of other species. Finally, 

 all known spores resist heat more strongly than the fully- 

 developed bacilli, but experiments have shown that these 

 degenerative forms are no more capable of resisting heat 

 than the tubercle bacilli themselves. 



As sh6wn in Fig. 66, 3, it is occasionally observed that 

 the bacilli present projecting processes or branches. The 

 frequency of this observation has changed our views of 

 the systematic classification of the organism, which proba- 

 bly is erroneously placed among the bacilli, belonging 

 more properly to the higher bacteria and being related 

 to the actinomyces. It is probably a streptothrix. 



The organism is not motile, and does not possess 

 flagella. 



While this statement is dogmatically made, there is 

 some evidence accumulating to show that the tubercle 

 bacillus is sometimes motile. Ferran ' and Schumowski 2 

 have observed a slow swimming movement. Ferran 

 even claims to have observed the flagella upon which the 

 movements depend. I have watched a pure culture of 

 the tubercle bacillus under the microscope, in the hang- 

 ing drop, and have seen a bacillus separate itself from its 

 fellows and sail off slowly and steadily. I am not sure, 

 however, that such occasional observations are con- 

 vincing, and prefer to consider the bacillus non-motile. 



The tubercle bacillus is peculiar in its reaction to the 

 anilin dyes. It is rather difficult to stain, requiring that 

 the dye used shall contain a mordant (Koch); but it 

 is also very tenacious of the color once assumed, re- 

 sisting the decolorizing power of strong mineral acids 

 (Ehrlich). 



This peculiarity delayed the discovery of the bacillus 

 for a considerable time, but, now that we are familiar 

 with it, gives us a most valuable diagnostic character, 

 for, with the exception of the bacillus of lepra and the 

 Bacillus smegmatis, none reacts in the same way. 



1 Sent, mid., 1897, No. 48. 



2 Centralbl f. Bakt. u. Parasitenk., May 20, 1898, xxiii., No. 19, p. 838. 



