Report on the Bacteriology of Water. 



247 



In all cases the Thames water experimented with contains an appre- 

 ciable, but not necessarily large, number of living bacteria, capable of 

 germination and growth on gelatine plates. As will be seen later on, 

 the above numbers are very small, no doubt owing to the low 

 temperature of the water, and the promptness of the cultures direct 

 from the river ; moreover, the number per 1 c.c, as shown by gelatine 

 plate-cultures, is to a great extent dependent on the temperature of 

 incubations. 



Series A. 



In this series of experiments I confined my attention to the 

 numbers of bacteria actually present in the Thames water when col- 

 lected. The method followed was the usual one of carefully collect- 

 ing the samples in sterile flasks, or occasionally in sterilised vacuum 

 tubes drawn to a point which is broken under the water by forceps : 

 these being heated and the glass point re-sealed in a spirit lamp at 

 the river itself. 



In no case given was the water allowed to stand more than a 

 couple of hours or so, and then at low temperatures, and in some 

 cases (employed as checks on the others) the plates were actually 

 made within half an hour of collecting. 



The method of making the plates was also the well-known one, 

 and does not need description here ; I employed round or square 

 Petri's dishes in all cases. 



Examples illustrating the results of these examinations are given 

 in Table A. 



Table A shows very clearly that the number of bacteria actually 

 present in the Thames water at the moment of collecting is not large, for 

 an open river, though differences appear to exist in June as con- 

 trasted with March and December as regards the numbers. I do 

 not propose to go into these differences at present, however, since 

 they are not striking, but it is worth noting that the experience of 

 previous observers favours the supposition that monthly differences 

 in the total number of bacteria of rivers are to be expected.* 



Of course the point could only be decided by continuous observa- 

 tion, which I think should be carried out. It is, perhaps, not 

 without interest to note that, so far as my few observations on this 

 point go, they bear out tbe conclusions of Miquel,f that there are 

 more bacteria in the river in March than in June, and more in Decem- 

 ber than in either of these months, a fact probably correlated with 

 tbe surface drainage and rain washings. I repeat, however, that 



* See, for instance, Miquel, 1 Manuel pratique d' Analyse Bacteriologique des 

 Eaux,' 1891, pp. 128 — 146, and the literature on rivers in our 1st Report, 

 f Loc. cit., pp. 131—133. 



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