178 PHARMACEUTICAL BACTERIOLOGY 



water (from roofs of houses) may have a smoky (creosote) odor or flavor 

 (drained from shingled roofs of houses) . Certain algae (Nostoc, Oscillaria 

 and others) may give rise to very disagreeable odors. Chemicals (perman- 

 ganate of potassium, hypochlorites, salt, lime) may impart a peculiar 

 taste and flavor. The containers (buckets, barrels, coolers, wood, leather, 

 canvas, etc.) may transmit special flavors. The odor may be garlicky 

 or otherwise disagreeable due to heavy sewage contamination. Pure 

 water is without taste, though it does produce a pleasing gustatary sen- 

 sation if cool and well aerated. The water in wells near large bodies of 

 salt water (ocean, bay, inland seas) may have a decidedly brackish taste. 

 Alkali seepage may impart a bitter or otherwise disagreeable taste. 

 The water of small mountain streams is usually highly contaminated with 

 decaying vegetable matter and frequently also contains decaying animal 

 matter. 



In the comparative sense, the highest contamination of bodies of water 

 prevails at or very near the shore, no matter whether the water is at rest 

 or flowing. The least contamination is found at points farthest removed 

 from the waters edge, the bottom and the surface. Gravitation soon car- 

 ries bacteria to the bottom, while some algae tend to accumulate near or 

 at the surface. In the case of flowing water, the gradual retardation of 

 the rate of flow, toward the shore, causes an accumulation of deposits along 

 the outermost edge of the stream. The intake end of the waterpipe of 

 the pumping station should be as near to the center of the water supply 

 as possible. 



The following is a tabulation of the more important contaminations 

 found in water supplies. 



I. Derived from soils indicating surface waters and surface seepage. 



1. Vegetable. 



a. Protococcus group. 



b. Desmids. 



c. Diatoms. 



d. Nostoc. 



e. Oscillaria. 



f. Yeasts. 



g. Molds. 



h. Spores of cryptogams, 

 i. Pollen grains, 

 j. Decayed vegetable tissues. 



2. Animal. 



a. Amebae. 



b. Paramecia, Spongilla, etc. 



