THE MULTIPLICATION OF MICRO-ORGAXISMS 229 



rate those which are non-volatile, can be obtained in a 

 concentrated form by evaporating a large volume (eight 

 to ten litres) of the water containing them at a low 

 temperature (30° to o5°C.); the concentrated solution 

 which remains is then found to be actually toxic to 

 some animals, and when introduced into waters pre- 

 vents bacterial multiplication taking place in the latter. 



It is very satisfactory to find independent experi- 

 mental confirmation of some of these interesting and 

 highly suggestive observations of Miquel's in the work 

 of the Massachusetts State Board of Health. In the 

 Eeport ^ of the latter, to which we have already referred, 

 experiments are recorded in which the power of multi- 

 ' plication of water bacteria is contrasted in one and the 

 same water before and after boiling. Thus a quart of 

 water from the City Service pipe was boiled in a clean 

 flask with a return condenser for one hour and so ren- 

 dered sterile. After cooling, it was mixed with 10 per 

 cent, of unboiled city water. A control flask was filled 

 with the same water unboiled, and both flasks, covered 

 merely with inverted sterile beakerSj were kept at the 

 same temperature. 



The following are the results obtained : — 



Boiled Water infected with Water Microbes 

 (Massachusetts Report) 



^ Eeport for 1890, p. 593. 



