848 RECORD OF CURRENT RESEARCHES RELATING TO 



It is probable that the method may bo well employed in examining 

 the tissues and liquids of animals for parasites. The author has thus 

 treated the Anurous Batrachia. 



On this subject it may be also noted that Professor Huxley has 

 recently thrown some doubt on the conclusions arrived at by chemists 

 in determining the wholesomeness of water. Organic matter may be 

 either of animal or vegetable origin, the former being dangerous, and 

 the latter much less so, if not altogether innocuous. To distinguish 

 between the two kinds is therefore all-important, but unfortunately it 

 is impossible directly to do this, as both animals and j)lants yield 

 albuminoid matters, which, chemically speaking, are practically 

 identical in composition. None of the processes in use by chemists 

 can be relied upon as giving any indication of the nature of the organic 

 matter, i. e. whether it is dangerous or not, and yet it is the almost 

 invariable custom to judge of a water by the quantity of organic 

 matter it contains, no matter what its origin, and a variation of two or 

 three times a given amount is held to make the difference between a 

 good and bad water. 



It was to this point that Professor Huxley especially addressed 

 himself at a meeting of the Chemical Society, and gave it as his 

 opinion, speaking as a biologist, " that a water may be as pure as can be 

 as regards chemical analysis, and yet as regards the human body be as 

 deadly as prussic acid, and, on the other hand, may be chemically 

 gross, and yet do no harm to any one." " I am aware," he said, " that 

 chemists may consider this as a terrible conclusion, but it is true, and 

 if the public are guided by percentages alone, they may often be led 

 astray. The real value of a determination of the quantity of organic 

 impurity in a water is that by it a very shrewd notion can be obtained 

 as to what has had access to that water." 



Mr. C. Ekin, commenting * upon these statements, says that since 

 chemical analysis fails entirely to distinguish between innocuous and 

 deadly kinds of matter, it may bo thought a work of supererogation to 

 have recourse to it at all. What, however, analysis fails to do directly 

 it can to a large extent do indirectly. Organic matter in solution in 

 water is more or less prone to oxidation, the highly putrescible matter 

 of sewage being most so, and that derived from vegetation being much 

 less so. Hence it follows that one would expect to find the oxidized 

 nitrogen compounds in a greater excess in the one case than in the 

 other, and that is what we do find. Almost invariably in all waters of 

 acknowledged wholesomeness the quantity of nitrates never exceeds a 

 certain small amount, whereas in polluted well and spring waters the 

 oxidized nitrogen compounds, with other accompaniments of sewage, 

 are to be found in excess. By means, then, of these oxidized nitrogen 

 compounds we get collateral evidence throwing light on the nature 

 and probable source of the contamination, of which a mere percentage 

 estimation of organic matter would fail to give the slightest indi- 

 cation. 



The mistake has been hitherto that the discussion has been 

 narrowed by looking at the question almost entirely from a chemist's 

 * See ' Nature,' xxii. (1880) p. 222. 



