TUBERCLE BACILLUS 215 



minute. It is quickly killed by formaline and corrosive subli- 

 mate, but resists 3 percent solution of carbolic acid for hours. 

 In sputum it withstands antiseptics for a long time. 



Chemical Activities. It grows slowly, producing no coloring 

 matter; yields an aromatic sweetish odor, but no gas or acid. It 

 produces certain plasmins or endo-toxins, which are called 

 tuberculins (q.v.). 



Chemically the tubercle bacillus contains two fatty matters, 

 one combined with an alcohol to form a wax. It has also a 

 protamin, a nucleic acid or an albumose. Various fatty acids 

 are to be derived from it by chemical treatment. The active 

 principle in tuberculin centers around its protein elements, but 

 is not exactly known. 



Habitat. It is a strict parasite and never leads a saprophytic 

 existence. Is found wherever human beings live in crowded 

 quarters; in dust of rooms, vehicles, and streets; and often in 

 milk and butter. It is very widely distributed, being found in all 

 human communities. 



Cultures. Since the organism does not grow below 3oC., 

 gelatine is never used. On coagulated blood serum of cows, 

 horses, and dogs, this bacillus grows best. As it is very difficult to 

 isolate in pure cultures, the following procedure should be followed : 

 The suspected sputum, fluid, or tissue is injected into a guinea 

 pig, and when, in two weeks or more, large swollen glands can be 

 felt in the groin, the animal should be killed, and a gland removed 

 under strict aseptic precautions. It is then divided, and the 

 halves containing the bacilli are rubbed over the surface of 

 coagulated dog serum and allowed to remain in contact with it. 

 The serum should be coagulated in special tubes, with glass caps, 

 having small perforations, which are stopped with asbestos fibre, 

 or glass wool. The organism grows well in air, but too great 

 access thereto dries and kills it. After the tubes are incubated 

 for a week or two, little scales growing unto clumps appear, 

 which are lobulated and friable. At first white, it later turns 



