836 MICROBIOLOGY OF DISEASES OF MAN AND DOMESTIC ANIMALS 



branes of the ch^st and abdominal cavities and upon various internal 

 organs. Cheesy abscesses may appear in the depths of soft organs. 

 In cows the udder is occasionally enlarged and shows hard masses 

 with little or none of the heat usually occurring in connection with in- 

 flammatory changes. Bones and joints are often involved especially 

 in the human; these structures increase in size, produce pain, and 

 suppurate. 



Bacterium tuberculosis is a slender rod-shaped organism with rounded ends and 

 under certain conditions shows granular forms. It varies between 2/j. and 5ju in 

 length, and 0.31* to 0.5/1 in width. This bacterium is usually straight, but may be 

 bent; it appears either singly or in groups or branched, non-motile, and is probably 

 not a spore producer (Fig. 174). Glycerin agar, blood serum, egg slant, and 

 bouillon may all serve as satisfactory nutrient media. It is aerobic and its tem- 

 perature limits for growth appear to be 29-42C. With the exception of young 

 and rapidly growing forms it is strongly acid-fast. Tubercle bacteria may be 



v 





FIG. 174. B act. tuberculosis. Branching FIG. 175. Bacterium tuberculosis. 



forms from a culture. (After Migula.} Sputum preparation uncolored. (After 



Migula.} 



demonstrated in cover-glass smears from diseased tissues and fluids and in tissue 

 sections (Fig. 175). In human tuberculosis the bacteria are frequently deter- 

 mined in the sputum, in bovine tuberculosis the bacteria may be occasionally dem- 

 onstrated in the nasal discharges and in the manure. Positive diagnosis may usually 

 be made by guinea-pig inoculation. For microscopic examination a cover-glass 

 smear is fixed in the usual way, then stained with hot carbol-fuchsin three to five 

 minutes or in cold stain fifteen to twenty minutes. It is then decolorized, e.g., 

 in 10 per cent nitric acid, and counterstained with methylene blue for about one 

 minute, after which it is rinsed and ready for examination. 



