Practical dairy bacteriology, prepared for the use of students, dairymen, and all interested in the problems of the relation of milk to public health . ater put the material again in a steam sterilizer,and sterilize for yi hour. t. 24 hours later sterilize again in steam fpr J^ hour. Thematerial,is now finished and may be preserved for future use. /. Agar slants. After the last steaming, while the agar inthe tubes is still hot and liquid, lay 20 of them down on a tablewith their mouths slightly raised so that the agar will form aslanting surface in the tubes. (Fig. 74.) Allow them to .hardenin
Practical dairy bacteriology, prepared for the use of students, dairymen, and all interested in the problems of the relation of milk to public health . ater put the material again in a steam sterilizer,and sterilize for yi hour. t. 24 hours later sterilize again in steam fpr J^ hour. Thematerial,is now finished and may be preserved for future use. /. Agar slants. After the last steaming, while the agar inthe tubes is still hot and liquid, lay 20 of them down on a tablewith their mouths slightly raised so that the agar will form aslanting surface in the tubes. (Fig. 74.) Allow them to .hardenin this position. LABORATORY WORK IN DAIRY BACTERIOLOGY 273 *No. 6. Determination of the Number of Bacteria in Milk. It is always first necessary to dilute the milk with sterilizedwater, since ordinary milk contains so many bacteria that, un-less diluted; the numbers will be too large, to be estimated prop-erly. Milk contains such a widely varied number, however, thatit is difficult to determine beforehand how much to dilute thematerial; and one must be guided, whenpossible, by knowledgeas to the age of the milk. Where a imiscellaneous lot of milk. FIG. 74^HARDENING AGAR SLANTS 1 is to be studied for this purpose, probably the best method isto dilute it 1,000 times. In order to dilute milk 1,000 or any other definite number oftimes, it is necessary to have flasks and vials measured to holdcertain definite amounts. It is most convenient to have someholding 4 , 9 , 19 and 99 (Fig. 75.) From themthe desired dilution can readily be obtained. a. Fill a number of these vials to the mark with water, plugwith cotton and sterilize. This can best be done in an autoclav.(Fig. 76.) In using this autoclav place a small amount of waterwithin it and then the vials to be sterilized. Replace the cover,fastening it down tightly with the screws designed for thepurpose, and light the gas. Leave the cock open until steambegins to comeout, and then close. Allowthe steam pressuretoirise
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Keywords: ., bookcentury1900, bookdecade1900, bookidcu319, booksubjectdairying
