IXOEGAXTC CONSTITUENTS. 20 



will hunt for water like any other animal susceptible of thirsty 

 sensations. 



Water not only carries into the system materials capable 

 of solution, but it holds in suspension substances which, in 

 some cases, are nutritious, but in others may be poisonous. 

 The purest water is not necessarily the best for man or 

 animals, and it is to the absence of some saline constituents 

 in mountain waters that cretinism has been ascribed in the 

 Alps. Dirty water is not necessarily injurious, but there is 

 probably no more prolific source of disease in man and animals. 

 This was proved in regard to cholera. Dr Lankestea: tells us, 

 in his interesting popular lectures: "In 1854 I was requested, 

 by the Vestry of the Parish of St James, "Westminster, to 

 examine the water from the pump in Broad Street, Golden 

 Square. The cholera had broken out there, and killed five 

 hundred people in less than a week, and the late Dr Snow 

 had accused the pump of doing all this mischief. Now I 

 detected nothing remarkable in that water but the filaments 

 of a fungus. It was a very curious fungus, and interested 

 me so much, that I published an account of it.* Its dis- 

 covery in the water led to .an investigation of the con- 

 dition of the well, and then it was discovered that the well 

 had for some time been in .communication with the cesspool 

 of an adjoining house, and subject to periodical overflows of 

 its contents. I have since seen these flocculent fungi in im- 

 pure water, and you will easily recognise them in the organic 

 contents of well-water and sewer-water. These fungi-form 

 filaments are accompanied with sombre, ugly-looking ani- 

 malcules, which are seldom found in pure water. There 

 is also an ill-favoured-looking little worm, much smaller 

 than a thread-worm, and belonging to the same family of 



* Quarterly Journal of Microscopical Science, voL iv 



