[14] Micro-organisms in Water (1894).
[15] Report on the Micro-organisms of Sewage, Reports to L. C. C., 1894, No. 216.
[16] Harben Lectures, 1896.
[17] Report on the Metropolitan Water Supply.
[18] The methods adopted for making a quantitative and qualitative examination of sewage are precisely analogous to those used in milk research. Dilution with sterilised water previous to plating out on gelatine in Petri dishes is essential (1 cc. to 10,000 cc. of sterile water, or some equally considerable dilution), otherwise the large numbers of germs would rapidly liquefy and destroy the film. Special methods must be used for the isolation of special organisms; phenol-gelatine, Elsner medium, indol reaction, "shake" cultures, Parietti broth, etc., must often be resorted to for special bacteria. Spores of bacteria may always be numerically estimated by adding the suspected water or sewage to gelatine, and then heating to 80° C. for ten minutes before plating out. This temperature removes the bacilli, but leaves the spores untouched.
[19] The bacilli of typhoid can live in crude sewage (Klein), but only for a very short period. When sewage is diluted with large quantities of water the case is very different. Bacillus coli flourishes in sewage.
[20] Annual Report of the Medical Officer of the Local Government Board, 1897–98, p. 210.
[21] John Tyndall, F.R.S., Floating Matter of the Air.
[22] Flügge has lately attempted to demonstrate that an air current having a velocity of four metres per second can remove bacteria from surfaces of liquids by detaching drops of the liquid itself.
[23] Hewlett and Thomson graphically demonstrated the bactericidal power of the nasal mucous membrane by noting the early removal of Bacillus prodigiosus, which had been purposely placed on the healthy Schneiderian membrane of the nose.