16 VETEEINAEY HYGIENE 



sediment or deposit as we see it which is harmful, but 

 rather that which is dissolved in the water of which the 

 sediment is only a probable index. Water may contain an 

 abundance of animal life and vegetable growth without it 

 being in any degree harmful. Bacteria innumerable may 

 be present and yet none of them pathogenic. In fact, the 

 probability of being able to hit off pathogenic organisms in 

 drinking water is very remote, owing to the extent of the 

 dilution. 



The deposit examined microscopically may consist of 

 living or dead vegetable matter, cotton or linen fibres, 

 fungi, algfe, diatomes, desmids, conferva, amcEbs, infusoria, 

 rotifera, water-worms, water-fleas, etc. ; while of animal 

 origin may be found epithelial cells, wool fibres, hairs, or 

 even muscular fibre. Besides these there may be found 

 various forms of bacteria, and the ova of parasites. 



Nothing very definite can be drawn from this examina- 

 tion ; epithelial cells, but especially muscular fibre, would 

 point to sewage contamination. From a veterinary point 

 the existence of ova, probably those of parasites, might 

 prove of the utmost importance. 



Bacteriological Examination is the only real method of 

 determining the nature of the micro-organisms found in 

 water, but it must be made by a specialist. A given 

 quantity of water is mixed with a nutrient medium, poured 

 out on a plate and allowed to grow at a suitable temperature. 

 Many colonies form on the plate and may be counted ; the 

 harmless organisms may be neglected, while those sugges- 

 tively pathogenic are further cultivated and identified. The 

 purer a water the fewer colonies found. 



Qualitative Examination of the Dissolved Solids. 



In the chemical examination of a drinking water, if any 

 turbidity or suspended matter exists, it must first be 

 removed by the process of filtration through paper before 

 the clear liquid is subjected to the process of testing. 



The following elements and acids are looked for, viz., 

 lime, magnesia, soda, potash, ammonia, iron, alumina, 



Digitized by Microsoft® 



