528 



Dr. P. F. Frankland. 



[June 10, 



of organisms and not pure cultivations are being dealt with, it is a 

 check which should on no account be neglected. 



Scope of the Experiments. 



The bacteriological examination by plate cultivation of a large 

 number of natural waters showed that practically all waters contain 

 micro-organisms in greater or less abundance, but that the number 

 found in such natural waters varies within exceedingly wide limits. 

 Thus whilst the number found in the rivers Thames and Lea usually 

 amounts to thousands in the cubic centimetre, that found in certain 

 deep well-waters, which I have had under continual observation, 

 rarely exceeds ten in the same volume. It appeared to me, therefore, 

 of interest to study the further history of the organisms present in 

 these waters of different origin and character. 



In the second part of the paper will be found a description of a 

 number of experiments made upon the power of multiplication pos- 

 sessed by certain pathogenic organisms, when placed under similar 

 conditions. 



I. Experiments with Micro-organisms present in Natural Waters. 



The waters which were made the subject of study are those sup- 

 plied by the eight Metropolitan Companies to London, and which for 

 various reasons are well adapted for purposes of experiment. Firstly, 

 they include waters derived from various sources, viz., from two 

 different rivers — the Thames and Lea — and from deep wells in the 

 chalk ; secondly, their chemical composition is well known, and is made 

 the subject of a very complete monthly investigation ; and thirdly, 

 their biological character has now been under periodical observation 

 for eighteen months past. 



Micro-organisms in Crude River-water. 



Samples of unfiltered river- water (temp. 2 a C.) collected in sterile 

 stoppered bottles were submitted to plate cultivation the day after 

 collection, whilst duplicate samples were allowed to stand at a tem- 

 perature of about 20° C. for five days, and then similarly examined. 

 The following results were obtained :— - 



Colonies found 



Description. Temperature. in 1 c.c. 



River Thames at Hampton Ferry r 



15th January, 1886 2° C. — 



Examined 16th January, 1886 ... 45,392 



Examined 20th January, 1886 ... 20° 35,790 



River Lea at Chingford, 15th 



January, 1886 3° — 



Examined 16th January, 1886 ... 39,307 



Examined 20th January, 1886 .. . 20° 63,488 



