304 PA THOGENIC BA CTERIA . 



or six weeks, and then killed. The autopsy is performed 

 according to directions already given. A large lymphatic 

 gland with softened contents or a nodule in the spleen 

 being selected for the culture, an incision is made into it 

 with a sterile knife, or a rigid sterile platinum wire is 

 introduced ; some of the contents are removed and 

 planted upon glycerin agar-agar, or, as Nocard and others 

 recommend, upon glycerinized potato. After receiving 

 the inoculated material the tubes are closed, either by a 

 rubber cap placed over the cotton stopper, which is cut 

 off and pushed in, or by a rubber cork above the cotton, 

 the purpose of this corking being to prevent evaporation. 

 The tubes must be kept in an incubator at the tempera- 

 ture of 37°-38° C. 



A very successful method of isolating the tubercle 

 bacillus has recently been published by Smith. 1 For 

 making the cultures dogs' serum is used. A dog is bled 

 from the femoral artery, the blood being caught in a 

 sterile flask, where it is allowed to coagulate. The serum 

 is removed by a sterile pipette, placed in sterile tubes, 

 and coagulated at 75°-76° C. Smith prefers to use a test- 

 tube with a ground cap, having a small tubular aperture 

 at the end, instead of the ordinary test-tube with the 

 cotton-plug. The object of this is to prevent the contents 

 from drying during the prolonged period of incubation 

 that is necessary. 



To the same end the ventilators of the incubator are 

 closed, and a large evaporating dish of water stood inside, 

 so that the atmosphere may be constantly saturated with 

 moisture. The tubes are inoculated with bits of tissue 

 the size of a small pea, torn from the tuberculous foci. 

 The fragments of tissue are not crushed or comminuted, 

 but are simply laid upon the undisturbed surface of the 

 blood-serum and then incubated for several weeks. If no 

 growth is apparent after this period, the bit of tissue is 

 stirred about a little and the tube returned to the 



1 Transactions of the Association of American Physicians, 1898, vol. xiii., 

 p. 417. 



