Practical bacteriology for chemical students / by David Ellis.

  • David Ellis
Date:
1923
Catalogue details

Licence: In copyright

Credit: Practical bacteriology for chemical students / by David Ellis. Source: Wellcome Collection.

    100/152 (page 88)
    It must be borne in mind that there are several varieties of this organism, but all possess the characters given above. The student is advised to consult more advanced and more specialised treatises for fuller information with regard to the varieties of Bac. coli communis. The identification of particular varieties is not required in the routine work of the bacteriological analysis of water. Exercise 70. The identification of Bac. coli communis. 1. Place a couple of drops of sterile water in a small sterile test-tube. Infect the water with Bac. coli. 2. Dip a sterilised Plat, loop into the infected water. 3. Make following cultures. (a) Nutrient-Agar. (b) Gelatine-stab. (c) Gelatine-plate. (d) Milk. (e) Lactose-broth. (f) Glucose-broth. Incubate a, d, e, f at 37 0 C. „ b and c at room-temperature. It will not be out of place at this point to place before the student a few figures from official statistics as a measure of guidance in the interpretation of his results. The watershed of the River Vyrnwy (tributary of the Severn) has been, formed into a large artifical lake by means of a dam. This lake is one of the main water supplies of Liverpool. A regular flow of water is allowed out of the dam and this of course flows into the Severn. Streams entering Lake Vyrnwy— One sample had 1 B. coli per c.c.: majority of streams showed purer water than that represented by 1 B. coli per c.c. Soil of watershed. B. coli absent in :i gram and in o -02 gram of soil. Number in larger quantities of soil not stated. Water of the Lake—Average number of bacteria of all kinds 31 per c.c. Here all results show a natural water practically free from pollution. The watershed is carefully protected from