examination of aie, soil, and water. 145 



Water. 



In the case of water, as in that of air, a knowledge of the 

 micro-organisms which may be present is not only of interest 

 to the bacteriologist, but of the greatest importance in practical 

 hygiene. Common putrefactive bacteria and vibrios may not be 

 hurtful in themselves, but they indicate the probability of the 

 presence of organic matter in which there may be danger. The 

 detection of Bacillus coli communis may be taken to indicate a 

 probable contamination with human excreta. 



The Microzyme Test which was introduced for the detection 

 of putrefactive bacteria, consisted in adding three or four drops of 

 the sample of water to 1 or 2 cc. of Pasteur's fluid, the nourishing 

 fluid having been previously boiled in a steriHsed test-tube. If the 

 microzymes or their germs existed in the water, the liquid in a few 

 days became turbid from the presence of countless bacteria. This 

 test is of no real value, for it does little more than indicate that 

 bacteria are present, which we know to be the case in all ordinary 

 water, and even in ice. On the other hand, the bacteriological test 

 of Koch is a most valuable addition to the usual methods of water 

 analysis. It enables us not only to detect the presence of bacteria, 

 but to ascertain approximately their number, and to study very 

 minutely their morphological and biological characteristics. The 

 importance of a thorough acqtiaintance with the life-history of the 

 individual micro-organisms cannot be too strongly insisted upon. 

 For example, by such means the spirillum of Asiatic cholera can 

 be distinguished from most other comma-shaped organisms, and 

 inasmuch as its presence may be an indication of contamination 

 with choleraic discharges, such water should be condemned for 

 drinking purposes, even though we are not yet in a position to 

 affirm that the microbe is the cause of the disease. The detection 

 of the bacillus of typhoid fever or of the Bacillus coli communis 

 in suspected water or milk would be evidence of considerable 

 importance. 



Koch's test, in short, consists in making plate- cultivations of a 

 known volume of water, counting the colonies which develop, 

 isolating the micro-organisms, and stvidying the characters of each 

 individual form. 



Collection and TroMsport of Water Samples. — Sternberg's bulbs, 

 or Erlenmeyer's conical flasks of about 100 cc. capacity, may bo 

 employed with advantage for collecting the samples of water. The 

 latter are cleansed, plugged, and sterilised in the hot-air steriliser. 



10 



