TUBERCULOSIS. 255 



cient access. Upon veal glycerin-bouillon the tubercle-bacilli 

 grow in the form of a superficial membrane, which exhibits the 

 same characters as the deposit upon glycerin-agar. In this also, 

 after the lapse of weeks under favorable conditions, after ten 

 days they reach the walls of the vessel, and likewise grow for 

 a certain distance upward upon the glass. The underlying 

 bouillon remains perfectly clear a feature that is characteristic 

 of the growth of tubercle-bacilli. 



Upon potatoes whose lower extremity projects into a solution 

 of glycerin (5 per cent.) and sodium chlorid (0.5 per cent.), the 

 tubercle-bacilli grow exceedingly well. Upon the surface of 

 the potato they form a dense deposit. The glycerin-solution 

 remains clear, and it is covered by the well-known coating. In 

 the preparation of such cultures it is best to employ the cyl- 

 inders of potato recommended by Roux. 



In the year 1892 Kitasato described a procedure suggested by 

 Koch for obtaining tubercle-bacilli directly from the sputum of 

 tuberculous patients. The patient should rinse his mouth care- 

 fully with an antiseptic gargle, and then expectorate into a ster- 

 ilized double dish. One of the masses of sputum ejected is washed 

 in several sterilized dishes containing sterile water, and is thus 

 freed from the bacteria adherent to its surface. From the central 

 portion of such a mass a flake is removed, by means of a platinum 

 wire, and smeared upon blood-serum in tubes. The cultures that 

 develop under these conditions exhibit quite a different appear- 

 ance than do those cultivated from the animal body. There 

 develop round, and rather whitish and translucent colonies, 

 which in subsequent generations grow in precisely the same 

 manner as the bacilli obtained by the method first described. 



Resistance of the Tubercle-bacilli. Tubercle-bacilli 

 are destroyed only after exposure for ten minutes to a tem- 

 perature of 70 C. (158 F.) ; for one minute, at a temper- 

 ature of 95 C. (203 F.) ; for an hour, at a temperature 

 of 60 C. (140 F.) ; and for four hours, at a temperature 

 of 55 C. (131 F.). They are, thus, more resistant to 

 heat than most other varieties of vegetative bacteria, which 

 are generally destroyed by brief exposure to temperatures 

 between 54 C. (129.2 F.) and 60 C. (140 F.). Tubercle- 

 bacilli resist for only a relatively short time the influence 

 of direct sunlight in accordance with the density of the 

 bacterial mass, from several minutes to several hours. 

 Diffuse daylight causes death after the lapse of a week. 

 Tubercle-bacilli can be cultivated for many years through 

 a series of generations, without loss of vitality, although 

 they gradually become somewhat less virulent. 



