290 



Till': W.VTKU-SL'l'l'LY OK TOWNS IN THK TKOIMCS 



The Bacterial 

 rtora of 

 tropical 

 water-supplies 



Bacterial 

 standard of 

 Daniels and 

 Finlayson 



1 tliiiik lius received but scanty notice — ^and that is, that if the subsoil contains much 

 clay, especially black day, in which there is a large percentage of organic matter, a 

 process of purification by natural filtration is impossible and there exists, indeed, 

 a culture medium. " Caution umst be exercised," he says, " when reliance is placed upon 

 the i)urifying property of the soil, especially if its characteristics be unknown, for the soil 

 is after all a filter, and all filters, whether artificial or natural, are treacherous, and are 

 a source of danger if not constantly attended to by some competent person." He also 

 comments upon the presence of disused wells in India and their use by natives for 

 insanitary purposes whereby the subsoil water is apt to be contaminated. 



Turning now to papers* dealing more exclusively with the bacteriological aspect of 

 the question we find Daniels^' and Finlayson reporting upon the natural waters of the 

 Federated Malay States. These are jungle streams, and Daniels remarks that the 

 organisms present in such water are abundant, and differ in type from those met with 

 in temperate climates or in tropical climates where the rainfall is less uniform and 

 vegetation not so rank. It is evident, therefore, that no general rule can be applied to 

 water-supplies in tropical countries as a whole. Each must be judged on its merits, 

 and it will be a long time before sufficient facts will have accumulated to enable us to 

 compare the waters of hot, dry, desert countries like the Northern Sudan with those 

 of steamy, humid regions where vegetation is rife and the rainfall is heavy. 



As regards samples of water taken from such jungle streams, Daniels considered it 

 advisable to consider as a basis : — 



1. The number of organisms exclusive of known, easily recognised, non-pathogenic 

 organisms, e.ij. B. sitbtilis, li. megaterium, B. prodigiosiii', B. violaceiis, and some of the 

 organisms which form characteristic yellow colonies which have been proved to be non- 

 pathogenic to lower animals. 



2. The amount of the water required to react, forming acid and gas, with MacConkey's 

 medium, from '2 c.c. to 2 c.c. being employed in the tests. 



3. Indol formation in 48 hours in peptone water with 10 c.c, 5 c.c. and 1 c.c. of 

 the water to be tested. 



As a standard the two observers suggested that; — 



1. Not more than 100 organisms, exclusive of those mentioned, should be present in 

 1 c.c. of the water. 



2. That no acid and gas should be formed in 24 hours in MacConkey's medium at 

 37° C. with 2 c.c. of the water. 



3. That no indol should be formed in peptone water in 48 hours with 5 c.c. of 

 the water added. 



They remark that the standard is not a high one but that it is exceptional to find 

 a natural water that will pass all thi-ee tests. In unprotected shallow wells, liable to be 

 polluted by surface washings, they found the average bacterial count to vary between 

 300 and 900 per 1 c.c, while in 23 out of 27 wells examined, acid- and gas-forming 

 organisms were present in 2 c.c. and usually in 4 c.c. of the water, and indol formers 

 in 5 c.c. in the case of ten of the wells. B. ■pijocyaneus was found in one instance, and in 

 two cases, organisms indistinguishable from B. coli communis. 



• The work of Kdwards" on the water derived from anus of the deltas of Philippine rivers, scarcely 

 merits consideration. l[c merely says that waters shonld be condemned (n) for the presence of animal 

 panisites ^4) for the i>resciiue of ]iatiiogenic l>actcria, and (i') when the <H>louy irount is above 2CH) per c.o. 

 .\ pajxjr by Dr. Katr.ik- ' ■ in tin- T,ifnsii,-i;„ns ,,i i/„; JJumbay Medical Vongicss (1309), is nlon^ s]>cciilative 

 than helpful. 



