Drinking- Water and some of its Im'purities. 117 



Taking the average of the first seven days we find it to 

 be 12°. 9 and of the last seven 10°. 9, a diff'erence of two 

 degrees, due, without doubt, to the inflowing rain and 

 snow water. 



A great source of pollution to water is sewage. Dr. 

 Frankland says, nearly the whole of the animal matter 

 which gains access to drinking-water consists of sewage, that 

 is, solid and liquid excrements." This is dangerous because 

 it contains decomposing organic matter. The products of 

 the decomposition of the animal matters are far more in- 

 jurious than those from the vegetable, and are highly in- 

 jurious even when present in minute quantities. These 

 impurities do not make themselves apparent to the taste, 

 but on the contrary, wells containing such waters frequently 

 acquire a wide spread reputation and people go a long dis- 

 tance for the waters which they regard as of a peculiarly 

 fine flavor. ^sTevertheless they contain an active poison. 

 Many diseases of the most fatal character are now traced 

 to the use of water poisoned with the soakage from soils 

 charged with sewage and excremental matter. Sudden 

 outbreaks of disease of a dysenteric character are often 

 caused by an irruption of sewage into wells, either from a 

 break in the sewer or from a cesspool, or from some pe- 

 culiarity of the season. Such contamination is not indicated 

 by any perceptible change in the appearance of the water. 



In Dr. Schuyler's Turkistan we find the following 

 account of a disease which is quite common among the 

 inhabitants where the water is bad. " The Sarts are not 

 only attacked by the usual maladies to which our frame is 

 heir, but they have besides two or three which are pecu- 

 liar to the country, or at all events very common there. 

 One of these is the reshta or Guinea-worm {Filaria medi 

 nensis) which is known also in several other parts of the 

 world where the climate is hot and the water bad. It is 

 probably produced by infusoria from bad water being 



