192 FILTER-BED NEMAS 



definitely suggestive. The filter-beds, after they have been cleaned 

 and again put to use, soon become the habitat of a succession of various 

 organisms, animal as well as vegetable, so that at the end of a period 

 of use it is no exaggeration to say that the sand through which the water 

 percolates swarms with them. To state a definite case quantitatively, 

 it has been shown during these examinations that such filter-bed sand 

 may contain hundreds of millions of nemas per acre in the top three 1 

 inches. Each of these nemas is excreting material of which the soluble 

 portions must pass into the city's water supply, and if in the course 

 of its passage through the filters, flumes, and delivery pipes this soluble 

 matter is not precipitated or otherwise altered, it is present in every 

 glass of drinking-water. 



FLAVOR OF DRINKING WATERS 



Drinking-water Connoisseurs? The excreta of any given filter-bed 

 organism must be different from that of any other, and though the 

 differences may be slight between similar organisms, there are good 

 reasons for thinking that the differences among the organisms of the 

 filter-beds of different cities are great enough to cause material dif- 

 ferences in the nature of their excreta. Such soluble parts of the excreta 

 as pass into the drinking-water must play a role in imparting to the 

 water its flavor and other qualities. This is enough to make one wish 

 that we had connoisseurs to assist us in the selection and control of 

 drinking-water, as we have connoisseurs in wine and tea, connoisseurs 

 or experts capable of distinguishing minute differences in the flavor of 

 drinking-waters. At first thought this may seem too fine-spun, and yet 

 when we think of the care exercised in selecting wines, teas, and other 

 beverages, and compare their actual importance with that of drinking- 

 water, it may not be going too far to suggest that consideration be 

 given to the possibility of determining th qualities of drinking-water 

 by flavor and other tests in addition to those now in use. I think 

 experienced persons with a delicate sense of taste will bear out the 

 statement that the drinking-water of each city has its characteristic 

 flavor. If half a dozen glasses of fresh drinking-water could be assem- 

 bled from the water supplies of as many cities, I have little doubt that 

 a person with a delicate sense of taste w r ould be able to tell one from 

 another blindfolded, at any rate where the differences were most 

 pronounced. 



In this discussion it matters little that the amount of the dissolved 

 substances thus suggested as a possible cause of differences in the physi- 

 ological action of drinking-water is minute, for it is a well-established 

 fact that very minute quantities of various substances may have a pro- 



