EXAMINATION OF WATER ng 



EXERCISE LXII 

 THE QUALITATIVE EXAMINATION OF WATER 



176. The qualitative examination of water consists in deter- 

 mining the species of bacteria present. From a sanitary stand- 

 point it consists in finding, if present, those species which may 

 be the cause of disease among people or animals consuming it. 

 The pathogenic bacteria which may be in the water will depend 

 upon the conditions ; but usually in this country water is exam- 

 ined for typhoid and hog-cholera bacilli, B. coli communis and 

 Ps. pyocyaneus. 



In India the spirillum of Asiatic cholera may be found in the 

 water. Occasionally anthrax may be suspected. It should be 

 stated that B. fluorescens liquefaciens, pseudo-typhoid, and the 

 transitional forms of the colon group are to be carefully differ- 

 entiated from Ps. pyocyaneus and B. typhosus. Owing to imper- 

 fect descriptions many of the common soil and water bacteria 

 cannot be readily identified. The genera are all that is ex- 

 pected here. 



References Frankland, Micro-organisms in Water. Fuller, 



Report Am. Public Health Asso., 1899, p. 580. 



177. Work for this Exercise. — Make at least 4 gelatin plate 

 cultures and such others as may seem necessary to deter- 

 mine the different species, especially of pathogenic bacteria 

 and their relative number in the specimen of water furnished. 



Read carefully the methods for water analysis in the text- 

 books. 



