ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
843 
Bacteriology of Water.* — Profs. P. F.Frankland and Marshall Ward 
have presented their first report to a Committee of the Royal Society 
on the present state of our knowledge concerning the bacteriology of 
water, with especial reference to the vitality of pathogenic Schizo- 
mycetes in water. 
They point out that the first fact to be firmly grasped is that water, 
as met with in actual life, is a very variable medium indeed ; it is 
probable, indeed, that no two samples of distilled water are absolutely 
alike in constitution, when the water distilled has been taken from 
different sources. The second fact of importance is that a Schizomycete 
is not only a very minute organism, but that it requires correspondingly 
minute traces of food material for its nutrition. Another, though less 
obvious, truth is that a Schizomycete is an extremely delicate organism, 
and it is a variable factor in itself, because it has a variable organ- 
ization. 
Water affects a living speck of protoplasm put into it, not only 
mechanically, but more especially physically and chemically ; the gases 
dissolved in the water exert pronounced effects ; any dissolved or sus- 
pended substances in the water must exert definite actions on the living 
organism ; the temperature of the water is of the utmost importance for 
the life or otherwise of any given species ; in some cases, at any rate, 
certain rays of light may complicate matters when they fall in sufficient 
quantity on water containing bacteria in suspension, or organic matters 
in solution. 
Distilled or pure water, as it is unknown in nature, offers little scope 
for practical enquiry, but may be used in check experiments. With 
sterilized water it is very different, for most observers agree as to the 
longer vitality of pathogenic forms in sterilized water than in the same 
water before sterilization. But whether water be sterilized by heat or 
by filtration, its constitution may be altered, but the latter method is 
certainly preferable to the former. With regard to the results of various 
observers, it is thought the numerical results obtained by the gelatin- 
plate method are, on the average, too low ; several workers have 
employed temperatures which are too high for comparison with what 
occurs in natural waters in this country ; many results have been 
vitiated by the introduction of very concentrated food materials with the 
pathogenic germs employed for infection. Conclusions drawn from 
experiments with distilled water must be received with great caution ; 
and in considering those from cultures in sterile waters, due regard must 
be had to all the facts, especially if the water was sterilized by heat. 
Neither mineral nor snow or rain water must be regarded as free from 
pathogenic germs capable of living ; in fact any water whatever may 
convey living pathogenic germs from one place to another. 
In all ordinary waters the rule is that the pathogenic forms die out 
sooner or later, with or without temporary multiplication. This final 
result is very commonly reached in three stages : — there is a preliminary 
diminution, due to the death of large numbers occasioned by the shocks 
induced by their altered environment ; there is a larger or shorter period 
of more or less active growth and multiplication ; and gradual diminution 
in numbers and vigour, as the available food-materials become exhausted. 
* Proc. Roy. Soc. Lond., li. (1892) pp. 183-279. 
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