7 
something to an analyst, but of what use is the mere fact 
that such and such an organism liquefies gelatine ? 
This briefly foreshadows the line of thought in this work ; 
we wish to study nature, not to attempt to fit nature into our 
laboratory ideas. If any facts in the life-history of fecal 
organisms can be established, we are at liberty to apply these to 
our work on water bacteriology. 
Something must be said on the subject of the method 
of analysis used in this investigation. The method which 
we shall make use of in this work is that suggested by Dr. A. 
MacConkey. It is not very different from that used in all 
other laboratories where bacteriological examination of water 
is carried out. A detailed description of the process will be 
found in appendix A. 
