630 MICROBIOLOGY OF THE DISEASES OF MAN AND ANIMALS. 



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; these increase 

 in size, produce pain, and suppurate. 



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

 varies between 2 j uand 5^ in length, and 0.3^ to 0.5^ in width. This bacterium is 

 usually straight, but may be bent; it appears either singly or in groups or branched, 

 and is probably not a spore producer. (Fig. 108). Glycerin agar, blood serum, egg 

 slant, and bouillon may all serve as satisfactory nutrient media. Tubercle bacteria 

 may be demonstrated in cover-glass smears from diseased tissues and fluids and in 

 tissue sections (Fig. 109). In human tuberculosis the bacteria are frequently deter- 

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



FIG. 108. Bact. tuberculosis. Branching 

 forms fom a culture. (After Migula.) 



FIG. 109. Bacterium tuberculosis. Sputum 

 preparation uncolored. (After Migula.) 



strated 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. 



It is conceded that tubercle bacteria do not multiply in nature outside 

 the animal body and therefore dissemination must depend wholly upon 

 the dissemination of infected man or animals and materials infected by 

 diseased man and animals. Tubercle bacteria escape from open ulcers 

 or from tubercular abscesses which connect with digestive or respiratory 

 organs. They may reach the surface in other ways; e.g., by the dis- 



