738 Tuberculosis 



method. They are motile and have flagella like the typhoid and colon bacilli. 

 They form no spores. Upon gelatin and agar-agar, circular colonies with a dark 

 nucleus surrounded by a transparent zone are formed. In gelatin punctures the 

 bacilli grow all along the line of puncture and form a surface growth with concen- 

 tric markings. The gelatin is not liquefied. The bacUli grow readily upon agar 

 and on potato, but without characteristic appearances. In bouillon a diffuse 

 turbidity occurs, with floating and suspended flakes. Milk is not altered. 



Pathogenesis. — The bacillus is fatal to mice, guinea-pigs, rabbits, hares, and 

 other rodents in about twenty days after inoculation. At the seat of inoculation 

 an abscess develops, the neighboring lymphatic glands enlarge and caseate, and 

 nodules resembling tubercles form in the internal organs. Similar bacilli studied 

 by Pfeiffer were isolated from a horse supposed to have glanders. 



