DRINKING WATER. 131 



a rapid and continuous drain, as for instance, during long and 

 severe work, the intervals between watering ought to be 

 proportionately decreased. 



Absorbed water is excreted chiefly by the skin, kidneys, 

 lungs, and in the recently delivered mare, by the udder. Un- 

 absorbed water is passed out with the dung. 



CONDITIONS WHICH DRINKING WATER SHOULD FULFIL. 



I. // should be free from injurious matter and kurtful 

 organisms. Among these we find decomposing organic (vege- 

 table and animal) matter, which is often derived from sewage ; 

 and infective microbes, which play a large part in the spread 

 of disease in the tropics, and a smaller though not an insig- 

 nificant one in temperate climates. Organic matter in drink- 

 ing water is of far less consequence of itself than the fact that 

 it renders water a favourable medium for the cultivation of 

 disease germs ; pure water being altogether unsuitable for that 

 purpose. We should not accept the presence of fish in water 

 as an unquestionable proof of its practical purity ; because 

 many species of coarse fish are able to thrive in water 

 which is unfit for horses to drink. In India and other 

 hot countries, stagnant water often contains large numbers 

 of thread-like worms (filarice), which produce various forms 

 of disease among horses. Neumann gives in his book on the 

 parasites of domestic animals (which has been translated by 

 Fleming) a full account of the serious effects on horses caused 

 by leeches entering their mouths while the horses are in 

 the act of drinking. The leeches (chiefly the Hcemopis 

 sanguisugd] which make this attack are generally young 

 ones which usually inhabit running water, and are seldom 

 longer than ^th of an inch. The streams and springs of 

 Algeria are greatly infested by them. 



2. // should be sufficiently aerated. When water is freely 

 exposed to the air, as in the case of rain, or when water 



9* 



