282 Recent Progress in Sanitary Science. 



It follows from what has been said, first, — that the album- 

 inoid-ammonia method neither indicates the absolute or rela- 

 tive amounts of organic impurities present, nor discriminates 

 between the putrescible and non-putreseible matters, with a 

 sufficient degree of accuracy to allow the results, obtained 

 by its use, to be employed in the formation of correct judg- 

 ments upon the potability of drinking waters. Moreover, 

 that analyses executed by this method must be thrown aside, 

 and replaced by others executed by the "combustion" pro- 

 cess. Finally, that until the results obtained in this more 

 accurate way are obtained, we are still destitute of data ade- 

 quate to the approval or condemnation of many sources of 

 water-supply at present suspected of dangerous contamina- 

 tion. 



With regard to the extent to which judgments founded 

 upon the chemical and microscopical analyses of drinking 

 waters are final, it may be said, that there can be no manner 

 of doubt that the resources of chemical analysis, at the pres- 

 ent time, are fully adequate to determine with accuracy the 

 amount of organic impurity which is actually present in a 

 potable water. Still more; it is possible to decide from the 

 amounts of nitrates, nitrites, and ammonia present in the 

 water — which bodies have been derived from organic bodies 

 preexistent, but are now converted into innocuous mineral 

 compounds — whether at a former period the water has been 

 polluted by sewage. But at this point the legitimate prov- 

 ince of the chemist ends, and that of the pathologist begins. 

 He must deeide by a careful analysis of the diseases attrib- 

 uted to the drinking of infected waters: — 1st. How large 

 an amount of organic impurity may actually exist, without 

 rendering the water noxious. 2nd. Whether water, which 

 at any time has been polluted by infected sewage, can be 

 afterwards employed with safety. 



In conclusion, I wish to present a report, which I was de- 

 puted to draw up in the capacity of Chairman of a Commit- 

 tee, being an attempt to formulate conclusions arrived at 



