192 



Profs. Percy Frankland and Marshall Ward. 



2. Bacteriological Examination of the Unsterilised JJnfiltered Thames 

 Water (First Series) after Infection with Anthrax. 



Table II brings out a number of points. In the first place the 

 extreme difficulty of discovering, by ordinary plate cultivation, a 

 particular micro-organism when present in only small numbers 

 alongside of vast multitudes of other forms," is particularly note- 

 worthy. Special reference was made to this difficulty in our First 

 Report, and it is most strikingly brought out in these experiments. 

 From the experiments made with the steamed and porcelain-filtered 

 Thames water, to be described below, we know that the number of 

 anthrax organisms in this unfiltered Thames water must have 

 amounted to at least 30 — 40 per cubic centimetre, yet only in one out 

 of the numerous plate cultivations made with this water was anthrax 

 discovered, and then only a single colony was found on a plate poured 

 on the day that the infection with anthrax was made. 



The principal obstacles to such discovery are two : firstly, in con- 

 sequence of the extremely large number of micro-organisms present 

 in the water, it is only possible to take a very small volume (not 

 more than, say, c.c.) for cultivation, in which, therefore, the 

 chance of anthrax organisms (if introduced in such small numbers as 

 in the present series of experiments) being present is very remote ; 

 whilst, secondly, owing to the rapid liquefaction of the gelatine 

 caused by many of these water bacteria, it is not possible generally 

 to incubate the plates for a sufficient length of time to admit of ihe 

 proper development of the anthrax colonies ; this is more particularly 

 the case when, as here, the anthrax is present in the form of spores, 

 which take time to germinate. 



In order to obviate these difficulties attending the discovery of 

 anthrax in the presence of large numbers of water bacteria causing 

 liquefaction, I have tried a number of special devices, of which 

 I need, however, only describe the one which proved the most useful. 



Previous experience had shown me that a large proportion of the 

 organisms present in water, and more especially those causing lique- 

 faction of the gelatine, are very sensitive to a temperature even con- 

 siderably below that of boiling water, whilst the spores of anthrax 

 in their normal state will withstand such temperatures for a con- 

 siderable length of time. 



In order to turn these properties to practical account, portions 

 (] c.c. or 3 c.c.) of the anthrax-infected Thames water under con- 

 sideration were mixed with a little sterile broth (1 c.c), and heated 

 for periods of two or five minutes to 50° C, to 70° C, and to 90° C, 

 after which treatment they were submitted to ordinary plate culti- 

 vation. The first of these experiments was made on March 31, 

 1892, and is recorded in the above Table II. The infected Thames 



