. A text-book of bacteriology; a practical treatise for students and practitioners of medicine. Bacteriology. THE PREPARATION OF CULTURE MEDIA 115 folding over one of its comers, and, applying the smooth end of a glass rod to the folded portion, gently pushing it into the mouth of the tube. After plugging and before media are introduced into the tubes and flasks, these should be sterilized. This is best done in one of the " hot- air sterilizers" (see Fig. 8, p. 69), by exposing the tubes for one hour to a temperature of 150° C. If greater speed is desired exposure to 180° to 190° C.
. A text-book of bacteriology; a practical treatise for students and practitioners of medicine. Bacteriology. THE PREPARATION OF CULTURE MEDIA 115 folding over one of its comers, and, applying the smooth end of a glass rod to the folded portion, gently pushing it into the mouth of the tube. After plugging and before media are introduced into the tubes and flasks, these should be sterilized. This is best done in one of the " hot- air sterilizers" (see Fig. 8, p. 69), by exposing the tubes for one hour to a temperature of 150° C. If greater speed is desired exposure to 180° to 190° C. for half an hour is usually safe. If by mistake, however, the temperature is allowed to rise above 200° C, a browning of the cotton plugs occurs and the glassware is apt to be stained by the burning of the fat and other organic material derived from the cotton. Petri dishes. Fig. 17.—Petri Dish. after cleansing are fitted together in the manner shown in Fig. 17, and are sterilized in the hot-air chamber at 150° C. for one hour. Glassware so prepared is ready for the reception of media. Ingredients of Culture Media.—The food requirements of bacteria have been discussed in another section. From what has there been said, it is apparent that artificial culture media must, to a certain extent, be adjusted to the peculiarities of individual bacteria. In the cases of the more strictly parasitic microorganisms growth can be obtained only by the most rigid observance of special requirements. For the large majority of pathogenic bacteria, however, routine or standard media may be employed, which, whUe slightly more favorable for one species than for another, are sufficiently general in their composition to per- mit the growth of all but the most fastidious varieties. The basis of many of our common media is formed by the soluble constituents of meat. These substances are best obtained by macerating 500 grams of lean beef in 1,000 of distilled water. The mixture is. Please n
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