Report on the Bacteriology of Water. 



313 



Part III. 



Joint Conclusions arrived at by both Authors. 



After carefully comparing the results, we beg to submit to the 

 Committee the following conclusions at which we have arrived on 

 the subject of inquiry : — 



1. The waters both of the Thames and of Loch Katrine normally 

 contain a number of different forms of micro-organisms, some of 

 which have been isolated and described (pp. 178 — 180, 186 — 191, 

 244—246, 285). 



2. These bacteria are, as far as our comparisons have been pur- 

 sued, more numerous in the water of the Thames than in that of 

 Loch Katrine, and the numbers in the Thames water at least have 

 been shown by us to be subject to well-marked seasonable variations, 

 being usually much greater in winter than in summer (pp. 178 — 180, 

 246) . This relationship is probably due to the Thames water in dry 

 weather being to a large extent derived from springs, whilst after 

 rain, especially in winter, it receives considerable accessions of surface 

 water rich in bacterial life and the organic materials which promote the 

 growth and multiplication of micro-organisms (pp. 178 — 180, 225). 



3. Hitherto no pathogenic bacteria have been found in the Thames 

 water, either by other observers or ourselves (p. 258). 



4. In agreement with the universal experience of all observers 

 who have given attention to the subject, we have found that the 

 water bacteria, both of the Thames and of Loch Katrine, multiply 

 with astounding rapidity when these waters are allowed to stand for 

 a few days, a maximum being rapidly reached, which is followed by a 

 corresponding, although less precipitate, decline (pp. 190, 191, 226, 

 249, 254.) 



5. An adequate explanation of this remarkable multiplication has 

 not yet been given, and is the more difficult to find, inasmuch as it 

 has been shown that the same phenomenon occurs in the case of 

 waters, like those of deep wells, which are almost wholly destitute 

 of organic matter. Again, although oxygenation and a high tem- 

 perature undoubtedly accelerate this multiplication, it even takes 

 place to a surprising extent at the low temperature of a refrigerator. 



6. We have experimented with the waters both of the Thames and 

 Loch Katrine in the three following conditions : — (1) in their natural 

 state as derived from the river and loch (p. 246) ; (2) sterilised, or 



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