CHAPTER LXV. 

 THE BACTERIOLOGICAL EXAMINATION OF WATER. 



Introduction. 



Section I. The collection and transmission of samples of water, p. 851. 



Section II. The methods of examination, p. 853. 



1. Enumeration of the organism, p. 853. 2. Determination of the nature of the 

 organisms present, p. 856. 3. Houston's method of water examination, p. 858. 

 The bacteriological examination of sewage, p. 861. 



A CHEMICAL analysis of water by showing the presence of organic matter, 

 nitrites, chlorides, ammonia, etc., will merely give a general indication that 

 a water is polluted. A bacteriological examination on the other hand will not 

 only reveal the fact that impurities are present in a water but will enable 

 the living organisms which it may contain to be enumerated, isolated and 

 identified. The detection of pathogenic micro-organisms in water is frequently 

 of the highest importance. 



The bacteriological examination of water may therefore be divided into 

 three parts : 



1 . The enumeration of the organisms present. Quantitative examination. 



2. The determination of the chief species present. 1 ^ ,-, ,- 



3. The isolation and identification of certain}- ^ uantai ; lve 



pathogenic organisms. [examination. 



With a view to avoiding the introduction of organisms from without certain 

 precautions are necessary in collecting a water for bacteriological examina- 

 tion, and moreover the sample must be transmitted to the laboratory under 

 such conditions as to prevent multiplication of the organisms in the water 

 before the examination is begun, otherwise the results of the enumeration 

 will be falsified. 



SECTION I. COLLECTION AND TRANSMISSION OF SAMPLES 



OF WATER. 



Collection. The water must be collected in a sterile vessel. In the majority 

 of cases 200-300 c.c. will be sufficient but in certain cases, as for instance in 

 searching for some of the pathogenic organisms, it is well to have 400-500 c.c. 

 The method of collection will be as follows : 



1. Take a new white-glass bottle of suitable capacity, rinse it out well 

 with water and after drying it plug it with wool and sterilize it. 



2. To collect the water for examination flame the mouth of the bottle, 

 remove the wool plug, fill the bottle as quickly as possible and plug with a 



