CHAPTER XXI 
THE TUBERCULOSIS GROUP 
Tuberculosis, or consumption, is an infection which 
occurs most often in the lungs, but no organ is safe; the 
bones, lymph glands, intestine, peritoneum, genital or¬ 
gans, skin, all frequently fall victims of the “white 
plague. ’ ’ 
I. Historical 
Koch, in 1882, was first to isolate and cultivate the 
bacillus. 
II. Morphology 
The bacillus is a slender rod, 2 to 4 /x in length. They 
are nonmotile, have no flagella, no spores, no capsules, 
but are said to have a cell membrane which enables them 
to resist drying. It does not stain with ordinary dyes, 
and a special method is used for the purpose (see chapter 
on Staining in General Bacteriology) ; because, once 
stained, it resists the action of strong acids, the tubercle 
bacillus is called “acid-fast.” It is Gram-positive. 
III. Cultural Characteristics 
The tubercle bacillus is very difficult to cultivate. 
Special media (described in chapter on Culture Media) 
are necessary for successful cultivation. Growth takes 
place from the tenth day on; when well developed the 
growth has a characteristic “bread crumb” wrinkled dry 
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