An introduction to the bacteriological examination of water / by W.H. Horrocks.
- Horrocks, W. H. (William Heaton), Sir, 1859-
- Date:
- 1901
Licence: In copyright
Credit: An introduction to the bacteriological examination of water / by W.H. Horrocks. Source: Wellcome Collection.
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![water from the Elbe, taken below Hamburg and Altona, showed that the greatest number of bacteria was obtained when O T per cent, of sodium carbonate was added to ordinary slightly alka- line gelatine-peptone. Dahmen, working with water from the Rhine, found that the addition of 0’15 per cent, of sodium car- ])onate to ordinary gelatine caused the development of the greatest number of micro-organisms. My own experiments with the South Hants water supply showed that more bacteria were obtained on alkaline than on acid media. Two batches of ordinary gelatine-peptone were prepared, one rendered just alkaline to phenol-phthalein, and the other to litmus. To the first batch N acid was added to the extent of 1*5 per cent., as recommended by the American committee, and to the second OT per cent, of sodium carbonate as suggested by Reinsch. Gelatine plates were then made with 0*5 c.c. of the South Hants water and incubated at 22° C. The following average results were obtained: 1 c.c. South Hunts witter. Acidiflecl Gelatine. Alkaline Gelatine. (I'o per cent. X acid.) (O'l per cent, sodium carbonate.) After 48 hours incubation at 22° C. ... 59 Colonies. ... 81 Colonies. ., 72 ,, „ 88 ,, ... 96. ,. On the fourth day the plates were usually destroyed by the liquefying organisms present in the water. All the water-organ- isms usually found in the alkaline media appeared to grow in the acid media, only a little more slowly. Hesse and Niedner recommend the following medium for the bacteriological exami- nation of water : Agar-agar . 1 •25 per cent. Albuinose (Heyden) 0’75 Distilled water 9S'00 This medium requires no correction for acidity or alkalinity, and permits the development of the greatest number of water- organisms. The authors consider that water-plates for the sinqile enumeration of colonies should be kept under observation for three weeks, as numerous experiments have shown them that at 20° C. in the first three days 00 per cent., in the first five days about 70 per cent., and in the first ten days about 90 per cent.](https://iiif.wellcomecollection.org/image/b28116525_0044.jp2/full/800%2C/0/default.jpg)
