218 Profs. P. F. Frankland and Marshall Ward. 



free from pathogenic germs capable of living, any more than it is to 

 suppose that water in the form of ice, snow, hail, or rain is incapable 

 of conveying infection during times of epidemics ; and that, in point 

 of fact, any water whatever may convey living pathogenic germs from 

 one place to another. 



(7.) That the periods through which pathogenic bacteria can live 

 in water vary according to a long series of circumstances, depending 

 especially on the nature and vigour of the germs, whether they form 

 spores or not, the chemical and bacteriological nature of the contents 

 of the water, the mode of contamination, and the temperature. 



(8.) That in all ordinary waters the rule is that the pathogenic 

 forms die out sooner or later, with or without previous temporary 

 multiplication ; very commonly this final result is reached in three 

 stages : (a) a preliminary diminution, due to the death of large 

 numbers occasioned by the shocks induced by their altered environ- 

 ment ; (b) a longer or shorter period of more or less active growth 

 and multiplication ; and (c) grad ual diminution in numbers and 

 vigour, as the available food materials become exhausted. 



(9.) As regards specific forms of pathogenic bacteria, existing 

 information extends chiefly to the following : — * 



Spirillum choleras asiaticee has been shown to live, and even multiply, 

 in drinking waters, though the results as to time are very conflicting ; 

 wbereas some found it dead after a couple of days, others state that 

 it lives a yearf in such waters. It is impossible to reconcile all the 

 statements ; the only points of general agreement seem to be that 

 cholera can be conveyed by water, and that it is, as a rule, not very 

 resistant towards the competing forms. 



Bacillus typhosus. — This seems to 'be much more resistant than the 

 cholera spirillum in most cases. Meade Bolton pointed out that it 

 needs far less organic material than cholera for its successful propa- 

 gation in water. The results of several observers point to its being 

 able to retain its powers for at least three months in drinking or 

 river waters ; but it seems to be eliminated more rapidly at higher 

 temperatures (above 18 — 20° C.) than at moderately low (8 — 12° C.) 

 ones. It may certainly be regarded as more able to hold its own 

 against the resident forms in bad waters than is the cholera spirillum, 

 and some results even suggest that the presence of other forms 

 favours it (Hueppe, Hochstetter) . Karlinski's andHolz's researches, 

 however, are decidedly opposed to this. J 



* See Appendix C for tabulated results. 



f Wolffhugel and Kiedel found the cholera bacillus alive in some cases after from 

 seven months to a year. Hochstetter gives 267 — 392 days. PfeifHer has similar 

 results. 



X See especially " Unters. iiber das Verhalten der Typhus-bacillen in typhosen 

 Dejektionen " (' Cent. f. Bakt.,' 1889, vol. 6, p. 65, and especially p. 75), and Max 



