. Agricultural bacteriology; a study of the relation of germ life to the farm, with laboratory experiments for students, microorganisms of soil, fertilizers, sewage, water, dairy products, miscellaneous farm products and of diseases of animals and plants. Bacteriology, Agricultural. GENERAL CHARACTERS OF BACTERIA 19 accomplish the purpose. Even boiling is not sufficient to destroy spores, so, to be sure of complete sterilization, a temperature above boiling is necessary. If the object is a solid that can bear heat it is simply heated at about soo^F. for an hour or so. If it is a liquid it is p
. Agricultural bacteriology; a study of the relation of germ life to the farm, with laboratory experiments for students, microorganisms of soil, fertilizers, sewage, water, dairy products, miscellaneous farm products and of diseases of animals and plants. Bacteriology, Agricultural. GENERAL CHARACTERS OF BACTERIA 19 accomplish the purpose. Even boiling is not sufficient to destroy spores, so, to be sure of complete sterilization, a temperature above boiling is necessary. If the object is a solid that can bear heat it is simply heated at about soo^F. for an hour or so. If it is a liquid it is placed in an autoclave (Fig. 12), and heat is applied until there is a steam pressure from 10 to 15 pounds. This produces a temperature sufficient to destroy spores. Sometimes it is desirable to ster- ilize Hquids that wiU not stand these high temperatures. This can be accompHshed by discontinuous heat. The material is heated to about i8o°F., or more commonly to boiling. It is then cooled and allowed to stand twenty-four hours in a warm place. The heat has destroyed the active bacteria, but has not killed the spores, which, during the twenty- four houri WiU ienninate and grow into active bacteria. Heat is again appKed as before, and this time any active bacteria that may have come from the germination of the spores are killed. The material is aUowed to stand another day so that any spores that may have failed to germinate the first day may grow, then heat is applied again. Experience shows that three heatings of this sort will destroy all the organisms and sterilize the liquid. To be successful in this method it is necessary that the interval between the heatings should be long enough for the spores to germinate, but not long enough for the bacteria arising from them to form any more spores. Twenty-four hour intervals have been found to be lie Fig, 12—An autoclave used in sterilization of liquids under pressure {Eyr),. Please note that these images are extracted from s
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbacteriologyagricult
