CHAPTER XXIX. 



Bacteriological Study of Water — Methods Employed — Precautions to be 

 Observed — Apparatus Employed, and Methods of Using It — Methods 

 of Investigating Air and Soil — Bacteriological Study of Milk — Methods 

 Employed. 



BACTERIOLOGICAL STUDY OF WATER. 



The conditions that favor epidemic outbreaks of typhoid 

 fever, Asiatic cholera, and other maladies of which these 

 may be taken as types, have served as a subject for dis- 

 cussion by sanitarians for a long time. 



Of the opinions that have been advanced in explanation 

 of the existence and dissemination of these diseases, two 

 should be considered: one, the ground-water doctrine of 

 von Pettenkofer, because of its historic interest; the other, 

 the belief that the diseases are disseminated by specifically 

 polluted waters, bacause it is the view now prevalent among 

 modern sanitarians. 



The advocates of the "ground-water" view explained 

 the occurrence of these diseases in epidemic form through 

 alterations in the soil resulting from fluctuations in the 

 level of the soil- water; and assigned to drinking-water 

 either a very insignificant r6le, or ignored it entirely. On 

 the other hand, those who have been instrumental in 

 developing the drinking-water hypothesis claim that altera- 

 tions in the soil play little or no part in favoring epidemic 

 outbreaks; but that, as a rule, they appear as a result of 

 direct infection, through the use of waters contaminated 



(603) 



