Etiology. 



505 



Fig. 77. Bac. Tuberculosis, acid- 

 fast form. Bronchial secretion 

 from cattle. Stained by Ziehl- 

 Nelssen's method. 



which. Spengler refers to as "splinters" and regards as true 

 spores,. 'Most investigators, however, look upon these bodies 

 as chromatin granules such as are found also in other bacteria 

 whether they are sporulating or non-sporulating species. 



Staining. The typical tubercle ba- 

 cillus is stained most readily and charac- 

 teristically with a warm carbol-fuchsin 

 solution or with any. aniline water gen- 

 tian-violet. After once absorbing the 

 stain the latter becomes so well fixed that 

 it is impossible to remove it with alcohol 

 or mineral acid (5% sulphuric acid — 

 30% nitric acid). This characteristic 

 (acid-fast or alcohol-fast) which is met 

 also in the bacillus of leprosy and in sev- 

 eral saprophytic bacteria, is due to the 

 presence of. fatty acids in the body of the 

 bacillus (Deycke) . No other bacteria ex- 

 cept those mentioned possess this charac- 

 teristic. 



Much's granular form of the tubercle 

 bacillus may be stained by Gram's method 

 of subjecting it to the action of aniline- 

 gentian violet for 24 to 48 hours at body 

 temperature. (See Diagnosis.) 



Culture. The tubercle bacilli will 

 grow only in the presence of oxygen and 

 at a temperature varying from 29 to 42° 

 C, its growth being most prolific at blood 

 temperature. The best culture media are 

 those containing egg albumen, although 

 the bacillus will grow also on common 

 laboratory media which do not contain 

 this substance. The chemical reaction of 

 the medium must be neutral or slightly 

 acid. The presence of glycerin, grape 

 sugar or phosphoric acid favors its growth 

 which is Usually very slow. Cultures are 

 never visible before the end of a period 

 of at least one or two weeks. 



On blood serum and on 3 to 5% 

 glycerin agar the cultures appear as fol- 

 lows: In the course of two weeks after 

 inoculation of material small gray dry 

 lusterless granules or scales make their 

 appearance. These are gradually sur- 

 rounded by a halo (Fig. 80). In the 

 course of time they form an irregular, 

 crumpled, dry granular continuous mass 

 which is easily removed from the surface 

 of the medium. On glycerin bouillon 

 after surface inoculation there is formed 

 a fine pellicle which ultimately develops 



Fig. 78. hac. Tuberculosis, gran- 

 ular form, Bronchial secretion 

 from cattle. Stained by Much's 

 u:ethod. 



Fig. 79. Bac. Tuberculosis, Stain- 

 ed by Hermann's method. (The 

 same material as in Fig. 77-78 ) . 



