Report on the Bacteriology of Water. 



215 



important points of all, the living Schizomycete is a variable factor in 

 itself, because it has a variable organisation.* When, therefore, we 

 place bacteria in water, we must not expect the resulting reactions to 

 be constant. 



The matter is obviously rendered still more complex when we turn 

 a given species of Schizomycete into a water already peopled with 

 aquatic (and, therefore, presumably well adapted) forms of different 

 species ; for the whole teaching of biology shows that the competing 

 organisms cannot exist side by side without affecting the welfare of 

 each. 



If we assume the simplest case, for the sake of argument, we have 

 to remember at least the following : — 



(1.) The water itself affects the living speck of protoplasm we 

 place in it, not only mechanically, but more especially physically 

 and chemically.f 



(2.) The gases dissolved in the water exert pronounced effects, as 

 is known from the relations of oxygen and carbon dioxide to plant 

 life in general, and from the effects of these and various other gases 

 on bacteria in particular. 



(3.) Any dissolved or suspended substances in the water must 

 exert definite actions on the living organism. This applies not only 

 to the minerals and organic substances in solution which are directly 

 useful as food materials, but also to products of metabolism or of 

 other chemical changes which are injurious to the life of the proto- 

 plasm of the microbe. Moreover, it applies to suspended particles 

 which exert surface attractions towards the suspended micro-organ- 

 isms, % or which affect the water in any way. 



(4.) The temperature of the water is, as has been seen, of the 

 utmost importance for the life or otherwise of any given species ; and 

 it requires but a moment's consideration to see that this factor exerts 

 an important influence on all the preceding. 



(5.) Although we are still very ignorant of the relations of light 

 to this subject, it is at any rate clear that in some cases at least 

 certain rays of light may complicate matters when they fall in suffi- 



* Proofs of this will suggest themselves to every biologist. We need simply 

 refer to Roux's experiments with anthrax (' Ann. de l'lnst. Pasteur,' 1887, 

 p. 392), and to those of Wolffhiigel and Riedel (' Arb. a. d. Kais. Gresundheitsamte,' 

 1886, p. 455) with cholera. 



f As regards this we may call attention to the plasm oly sis experiments of De 

 Vries, Pfeffer, Fischer, and Wladimiroff already referred to on p. 198. 



X There is a large literature on this subject (and the allied one of nitration). 

 See Percy P. Frankland (" The Removal of Micro-organisms from Water," ' Roy. 

 Soc. Proc.,' 1885, pp. 379—393), and Kriiger (" Physikalische Einw. v. Sinkstoffen 

 auf die im Wasser befindl. M'organismen," ' Zeit. f . Hyg.,' vol. 7, 1889, pp. 86 — 

 114) ; also Duclaux (" Le Filtrage des Eaux," 'Ann. de l'lnst. Past.,' 1890, pp. 41 — 

 46) , where other references are given. 



VOL. LI. Q 



