v] METHODS OF INOCULATION 79 



Of the above distribution then, to each phenol gelatine 

 or phenol broth tube -j or ~ cc. is added, the gelatine is 

 shaken and poured out into a plate, and after setting kept at 

 20° C, the phenol broth is incubated at 37° C. From the 

 phenol broth incubated for twenty-four hours, plates in 

 phenolated gelatine are then made. If in the original water 

 the bacillus coli or the sewage variety of proteus Zenkeri or 

 the typhoid bacillus be present, the phenol broth-cultivation 

 will be found uniformly turbid after twenty-four hours' in- 

 cubation ; by placing a droplet of this culture into 10 cc. of 

 sterile salt solution and making with a platinum loop of this 

 dilution a phenol gelatine plate, this after incubation for 

 two to three days will show either of the above organisms in 

 numerous colonies. 



The phenol gelatine plates when ready —after two to 

 four days' incubation at 20° C. — must be carefully examined, 

 and all the surface colonies which resemble in aspect the 

 above organisms have to be tested by fresh preparation, by 

 flagella staining, and by subcultures in different media. 

 Of this more when we come to deal with the differential 

 characters of the bacillus coli and typhoid bacillus. The 

 sewage variety of the proteus Zenkeri, as will be also de- 

 scribed later, is in its surface colonies so characteristic and 

 conspicuous that this and the microscopic examination are 

 sufficient for diagnosis. 



Another method is this : mix in a sterile flask equal 

 volumes — 50, 100 or 200 cc. — of the water and broth, 

 having added to the latter the required quantity of phenol, 

 then incubate the flqsk at 37" C. for twenty-four hours, 

 and make phenol gelatine plates as before. 



By these methods I was enabled to demonstrate the pres- 

 ence of an abundance of the typical bacillus coli not only 

 in Thames water above Hampton, that is the intake of the 



