INFECTIOUS DISEASES 



331 



long and .3 to .5 micron in width, and is usually curved or slightly 

 bent. It may contain granules or the body may be uniform. It is 

 nonmotile and does not form spores. This organism is covered with a 

 waxlike substance which renders it more difficult to stain than ordi- 

 nary bacteria, but after the organism has been stained, which can be 

 accomplished by applying' steaming carbolfuchsin for five minutes, it 

 retains the stain even when subjected to the action of acids ; for this 

 reason it has been called an acid-fast bacterium. It is an aerobe, and 



Tuberculous focus in spinal process of a dorsal 

 vertebra 



Tulierc-ulous 



focus in body 



of dorsal 



vertebra 



Fig. 96. Vertebral tuberculosis in the hog. (Ostertag.) 



grows with relative .slowness. It grows luxuriantly in egg albumen 

 culture medium, and fairly well on glycerine agar and in glycerine 

 bouillon. Tubercle bacilli from different sources manifest different 

 cultural characteristics, and on this basis some have claimed four 

 varieties of tubercle bacilli, namely, human, bovine, avian, and rep- 

 tilian.. The bovine and human types have been encountered in swine. 

 ■ The tubercle bacilli are very resistant to external injurious influ- 



