BACTEKIAL CONTENTS OF VARIOUS WATERS 87 



These figures show again how very variable are the 

 bacterial contents of ice, not onlyjwhen derived from 

 different sources, but also in those samples collected 

 from one and the same place. 



Heyroth states that to avoid all chance of the dis- 

 turbance of his results by esiternal contamination, he 

 first broke up the ice, and then abstracted with sterile 

 forceps a good-sized piece out of the middle of the 

 block, which was thoroughly | washed with hot sterilised 

 distilled water, so as to melt the surface of the lump of 

 ice, and ensure with still more certainty the absence 

 of any accidental pollution. The piece to be ex- 

 amined was then slowly melted in a sterile test-tube, 

 and 1 c.c. of the ice-water submitted to gelatine- 

 plate cultivation. 



Bordoni Uffreduzzi^ has made an examination of the 

 number of micro-organisms present in ice supplied to 

 Turin. The water for this purpose is collected from 

 the river Dora, and is frozen and supplied by various 

 companies to the city. It was found that whereas 

 the river water contained innumerable micro-organ- 

 isms in the cubic centimetre, the ice derived from 

 the same water contained on an average 580 microbes 

 in the cubic centimetre. It should be mentioned that 

 these ice companies abstract their water from two 

 different places, some from the river before it enters 

 the cit3^, others from a point lower down and after it 

 has received pollutions from the city. The above 

 average result was obtained from the purer river 

 water. 



Although, according to Uffreduzzi, the ice always 

 contained 90 per cent, less organisms than the river 

 water, yet this reduction is not sufficient to render ice 



^ 'Die biologiscbe Untersuchung des Eises,' Centralhlatt filr Bak- 

 teriologie, vol. ii. p. 489. 



