744 THE MICROSCOPE. 



desirable that those who are called upon to advise on 

 snch matters should be able to appreciate the chemist's 

 arguments, and criticize his data. To do so properly 

 we must know something of the theory of water 

 analysis, and must bear in mind, or have at hand, the 

 arbitrary standards which experience suggests as valu- 

 able in classifying waters. 



It is perfectly clear, however, that the organic 

 matter found in water that known to be most detri- 

 mental to health is completely destroyed by chemical 

 analysis, and, therefore, the conclusion arrived at by 

 the chemist as to the wholesomeness of water is either 

 misleading or entirely fallacious. 



The organic matter in water may be either animal or 

 vegetable, or the two may be combined ; the first being 

 the more dangerous contamination, and to distinguish 

 between the two kinds is, after all, important. Both 

 animals and plants yield albumen ; and, chemically 

 speaking, albuminoid matters, whether of animal or 

 vegetable origin, are practically identical in composi- 

 tion. It is an admitted fact that " chemical analysis 

 is one of the poorest things possible to rely upon as 

 giving a true indication of the actual nature of organic 

 matter, much less to reach the delicate quantities which 

 show that a particular specimen of water is free from 

 sewage or infective organisms." No analysis of water 

 can be pronounced complete without having been first 

 submitted to microscopical examination. For the detec- 

 tion of living organisms, and of germs believed to set 

 up disease in the animal body, we must at all times 

 have recourse to the microscope. The determination 

 of the organic impurity of water by the microscope 

 is of immense value, as by its aid we are in a position 

 to say what has had access to it, and thus approximately 

 measure its unwholesomeness. 



The mode of examining specimens of water is as 

 follows : A Winchester quart bottle at least should be 

 taken and stood by, in a warm, quiet place, for twenty- 

 four hours. If, after standing twenty or thirty hours, 

 no great amount of deposit is thrown down, recourse 

 should be had to other means of collecting the suspended 



