THE WATEE-SUPrLY OF TOWNS IN THE TROPICS 317 



in the report {;page 310) is not hurtful and does not appear to taint the water, under 

 any known conditions, its multiplication, as shown by bacteriological examination, is 

 favoured by this "dead-end" system. 



When it cannot be detected in small quantities of water taken at the wells it can be 

 easily found in similar amounts taken from taps at various points on the pipe system 

 (vide infra). At the same time its presence has no special significance although one 

 would be better pleased if it were absent altogether. 



The stagnation can be overcome by occasionally flushing out the pipes by hydrants Stagnation in 

 at the " dead-ends," but naturally this involves a waste of water, especially when it has '^«''°"''™^- 

 to be frequently done to clear the pipe system of crenothrix growth, discoloured water or with 

 water which, if left alone, might possibly acquire an unpleasant smell or taste from the 

 presence of the gas-forming bacillus. It is, however, only fair to say that laboratory 

 experiments on a small scale have not shown any signs of risk in this last direction. 

 One gives here the moi'phologieal characteristics and pathological effects of the organism 

 in question. These were not fully discussed in the paper. 



It was found to be a short, motile rod. Gram-negative, but staining readily by the 

 ordinary aniline dyes. Its chief cultural characteristics were as follows :— 



On agar slope it produced slimy, grey colonies with thin bluish-green margins, and 

 it soon coloured the medium a bright green colour. The colonies had a bad smell similar 

 to those of the proteus group. Neutral red was reduced with a yellow fluorescence, gas, 

 but not in large amount, was produced in a glucose medium, and certain strains, also 

 fermented lactose ; but this was not a constant characteristic. In liquid media, a thick 

 scum was produced. The colonies on Drigalski-Conradi were thick, slimy, dark greenish- 

 blue and evil-smelling ; on Endo they were pinkish-red — not unlike those of B. coli, but 

 spreading with a beautiful violet fluorescence ; on lactose bile-salt agar they were, as a 

 rule, a greenish-blue with well marked fluorescence. 



Indol was produced in appropriate media, while in litmus whey the colour was, as a 

 rule, discharged. The effect on litmus milk varied. Sometimes the medium remained 

 unchanged, sometimes the milk clotted and was afterwards liquefied, sometimes considerable 

 alkali was produced. On potato a dull slimy brown growth developed, and the jDotato was 

 coloured a deep green. Blood serum was rapidly digested. 



The organism was not pathogenic for guinea-pigs or fowls, but killed jerboas and 

 gerbils speedily, both when injected subcutaneously and intraperitoneally. 



Appended will be found an account of the bacteriological examinations conducted on Bacteriological 

 tap waters in different parts of the town. It will be seen that there is always a '=';^"i'"^"°"^ 



'^ ot tap waters 



considerable multij)lication in the number of colonies and that some form of gas-producing 

 organism — usually the green lactose fernienter — is almost invariably present in the 

 quantities examined. 



Eleven examinations of tap water in Khartoum were made between May, 1909, and 

 January, 1910. The average colony count was 50 per 1 c.c. The locality did not seem 

 to influence the count. There were fewer colonies in the Grand Hotel water than in 

 the Palace water which is only about half as far from the source of supply. 



In eight instances the chromogenic, lactose-fermenting bacillus was found. In one 

 instance an atypical Bacillus coli was found. 



In one instance a non-chromogenic, lactose-fermenting, proteus-like organism was 

 found. In the remaining case no gas-forming, sugar-feimenting organism was found. 



At present local distribution is carried out in two ways. In the first and second 

 class quarters of the town, meters have been installed and the water is laid on to the 



