82 



MANUAL OF BACTERIOLOGY. 



FIG. 18. 



bouraud recommends the following for the cultivation of 

 the trichophyton fungus : 



Peptone 5 grams. 



Maltose 3.8 grams. 



Agar 1.3 grams. 



Water 100 c.c. 



Test-tubes. Bacteria are generally cultivated in test- 

 tubes. A convenient size is one f of an inch in diameter 

 and 5 inches in length. The tubes 

 should be of a heavier glass than in 

 those used for ordinary chemical work. 

 The New York Board of Health, and 

 some others, use a tube three inches 

 in length without a flange for the cul- 

 tivation of the diphtheria bacillus on 

 Loffler's blood-serum mixture. Test- 

 tubes should be thoroughly cleaned with 

 a swab before using; they should be 

 boiled with washing-soda, rinsed, 

 filled with hydrochloric acid solution, 

 rinsed, and inverted to drain away the fluid. 



Plugs of raw cotton or cotton batting are employed as 

 stoppers. Some prefer absorbent cotton, but it is likely to 

 become soggy after exposure to steam. The plug should fit 

 smoothly; creases and cracks around the edges are to be 

 avoided. The plug should be tight enough to sustain the 

 weight of the tube when held by the plug. These plugs pre- 

 vent bacteria from entering or leaving the tubes. 



Sterilization of Test-tubes. The tubes are to be steril- 

 ized in a hot-air sterilizer for one hour, at a temperature 

 of 150 C. The cotton should acquire a light brown color 

 but should not be burned. If the plugs touch the sides of 

 the sterilizer or lie against the bottom they may be scorched. 

 The necessity for sterilization of the tubes before filling 



Wire Basket for Test- 

 tubes. 



