194 BACTERIA 



quickly killed by formaline and corrosive sublimate, but resists 

 3 percent solution of carbolic acid for hours. In sputum it with- 

 stands 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 tuber- 

 culins (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. Has also been observed in the tissues and secretions 

 of non- tuberculous persons. It is very widely distributed, being 

 found in all human communities. 



Cultures. Since the organism does not grow below 30 C., gela- 

 tine 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 con- 

 taining 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 per- 

 forations, which are stopped with asbestos fiber, 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 into clumps appear, which are lobulated and friable. 



