Essentials of bacteriology; being a concise and systematic introduction to the study of bacteria and allied microörganisms . -Flask toblood-se- NUTRIENT CULTUEE-MEDIA 73 having been placed in the thermostat, are kept at a temper-ature of 65° to 68° C. mi to. coagulation occurs; then removedand sterilized by fractional sterilization. Sterilization of Blood-serum.—^The tubes are placedthree to four days in incubator at 58° C, and those tubeswhich show any evidences of organic growth are discarded. If, now, at the end of a week, the serum remains sterile at. Fig. 21.—^Thermostat or inspissator f
Essentials of bacteriology; being a concise and systematic introduction to the study of bacteria and allied microörganisms . -Flask toblood-se- NUTRIENT CULTUEE-MEDIA 73 having been placed in the thermostat, are kept at a temper-ature of 65° to 68° C. mi to. coagulation occurs; then removedand sterilized by fractional sterilization. Sterilization of Blood-serum.—^The tubes are placedthree to four days in incubator at 58° C, and those tubeswhich show any evidences of organic growth are discarded. If, now, at the end of a week, the serum remains sterile at. Fig. 21.—^Thermostat or inspissator for blood-serum. the ordinary temperature of the room, it can be used forexperimental purposes. Perfectly prepared blood-serum is transparent, of a gelatin-like consistence, and straw color. It wUl not liquefy by heat,though bacteria can digest it. Water of condensationalways forms, which prevents the drying of the serum. Short Method.—Blood-serum may be prepared in a shorter 74 ESSENTIALS OF BACTERIOLOGY way by coagulating the serum at a temperature short of boil-ing-point. Sterilization is completed in three days by expos-ing the tubes to a temperature of about 90° C. each day forfive minutes. Tubes so prepared are opaque and white. Preservation of Blood-serum in Liquid State.—Kirchneradvises the use of chloroform. To a quantity of serum in a well-stoppered flask a smallamount of chloroform isadded—^^enough to form abouta 2 mm. layer on the bot-tom. If the chloroform isnot allowed to evaporate,the serum remains sterUefor a long time. When
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