A laboratory guide in elementary bacteriology / by William Dodge Frost.

Date:
1903
Catalogue details

Licence: In copyright

Credit: A laboratory guide in elementary bacteriology / by William Dodge Frost. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    Sodium chloride Peptone (Merck) i. Potassium nitrate 0.2 “ - Filter, tube and sterilize, 3 tubes. Water 1,000. gms. h. Litmus Milk. 1) Freshly separated milk, or if this is not available, new milk is placed in a separatory funnel in an ice chest over night to allow the separation of the cream and the milk then drawn off. 2) Litmus solution (e. above) is then added until medium is faintly blue. 3) Tube and sterilize in the steamer for 30-45 minutes on 3 or 4 consecutive days. During the summer months particularly very resistant bacterial forms abound in the milk, so that it is necessary to increase the number of applications or length of exposure. The efficiency of the sterilizing process should be tested by placing the milk in the incubator for several days to see if any change occurs, 2 tubes. In addition to the above have 15 tubes of bouillon (9 to contain exactly 10 cc. for 41. and 44.) 10 tubes of gelatin, 15 tubes of agar, 6 water-blanks and 5 potato tubes. (If thought desirable the media required for Chapters IV. and V. [Exercise 58], may be prepared at this time; this would then com- plete all the media making required in Part I.) EXERCISE 38. EFFECT OF REACTION OF MEDIA ON GROWTH. General Directions. a. Melt 6 tubes of gelatin and add, under aseptic precautions, to three of them, respectively, 0.1 cc., 0.3 cc., and 0.5 cc. of a normal solution of hydrochloric acid, and to the other three the same amounts of a normal sodium hydrate solution. b. Thoroughly mix, solidify gelatin in ice water and then inocu- late (stab) each tube with the organism to be studied. c. Make a control culture in a tube of neutral gelatin. cl. Incubate at 18° C. and note the effect of the chemicals on the rate, amount and character of the growth. References. L. & N. 35; McF. 41. Special Directions. Use B. subtilis and B. coli. Make sketches. EXERCISE 39. EFFECT OF CONCENTRATION OF MEDIA ON GROWTH. a. Pour about 2 cc. of “condensed milk” into each of two sterile test-tubes, dilute one with five times the volume of sterile water.