430 THE TUBERCLE BACILLUS GROUP 



The tubercle bacillus is non-motile and possesses no flagella. It 

 forms no capsule but possesses a waxy envelope which confers upon 

 the organism unusual resistance to desiccation and to the action of 

 chemicals. No spores have been definitely demonstrated, but Koch 1 

 believed that the deeply staining granules found in the bacillus might 

 be true endospores. The generally accepted view is opposed to this 

 supposition. 2 



Staining. Tubercle bacilli and closely related organisms possess 

 in common a relatively large amount of waxy substance 3 which is 

 relatively impervious even to the more intense stains, as carbol-fuchsin. 

 Ordinary anilin dyes do not stain members of the tubercle bacillus 



FIG, 61. Tubercle bacilli, beaded forms. 



group. They are Gram-positive, but it requires several hours for the 

 anilin-oil gentian violet to color the organisms. When a stain has 

 penetrated the substance of the tubercle bacillus it is retained with 

 great tenacity; alcohol and even rnineral acids in moderate concen- 

 tration fail to remove it except after long exposure. The members 

 of the tubercle bacillus group vary somewhat in this resistance to 

 decolorization; the true tubercle bacilli are both "alcohol-" and 

 "acid-fast;" other organisms in the group may be either "alcohol-" 

 or "acid-fast." Young tubercle bacilli are frequently non-acid-fast. 4 



1 Mitt. a. d. Kais. Gesamte, 1884, ii, 22. 



2 See Wherry, Centralbl. f. Bakt., Orig., 1913, Ixx, Heft 3-4. Conditions which favor 

 the formation of "spores" in certain acid-fast bacteria. 



3 For chemical composition of fatty substance of the tubercle bacillus see: de 

 Schweinitz and Dorset, Jour. Am. Chem. Soc., 1898, xx, No. 8, p. 618; 20th Annual 

 Report, Bur. Animal Ind., 1903. Levene, Med. Record, December 17, 1898, 873; 

 Jour. Med. Research, 1901, vi, 120; 1904, xii, 251. Kresling, Centralbl. f. Bakt., 1901, 

 xxx, 897. 



4 Wolbach and Ernst, Jour. Med. Research, 1903, x, No, 3. 



