1893.] MICKOSCOPICAL JOUKNAL. 135 



scopical- — in order to really encompass anything like the whole of 

 the many difficult questions which it involves. 



The tendency of the present day is to individualize the various 

 sources of contamination, the dream of the biological investigator 

 being, at any rate, that, through study of the life history and 

 pathogenic effect of the numerous species of minute life which 

 we now know inhabit all waters, we may finally determine, largely 

 by the aid of the microscope, whether or not any given water 

 supply contains anything deleterious to health. In the view of 

 this class of investigators, the microscope is of quite as great or 

 even greater importance in water examinations than the chemist's 

 more elaborate array of retorts and appliances for determining 

 equivalent volumes. This view, too, it may be said, is now 

 generally held by advanced chemists, and we accordingly find 

 sucli using the microscope as a check on the otherwise uncertain 

 indications of the chemical analysis. It should not be overlooked, 

 however, that the four distinct lines which have been already 

 indicated should be pursued in any case where a complete sanitary 

 analysis is desired, and hence the rational statement of the matter 

 is that the microscopical examination takes equal rank with the 

 chemical. The author, in the course of a somewhat extended study 

 of sources of water supply, has had occasion to frequently decide 

 the question of relative sanitary value of different sources, and has 

 yet to see the case where an intelligent use of the microscope in 

 conjunction with a study of the environment would not furnish 

 decisive evidence on which to decide for or against. The method 

 of examining a source of proposed water supply which he has 

 found the most satisfactory is to spend some little time tramping 

 over the drainage area with a portable outfit for the microscopi- 

 cal examination as his only companion. A sample can be taken, 

 filtered, and the enumeration made in an hour or an hour and a 

 half from the time of taking. In this way we learn to a certainty 

 the actual number of forms of minute life present, there being 

 absolutely no opportunity for changes to take place. That this 

 point is of considerable practical importance will be readily ap- 

 preciated after one has collected a few samples in mid summer, 

 one portion being examined at once and the other left standing for 

 one or two days before the examination. In the latter case the 

 microscope will be very likely to show large quantities of amor- 

 phous matter which will not appear in the portion examined im- 

 mediately after collecting. Nor is this all. If the same portions 

 are examined chemically, it will be found that the proportionate 

 amounts of free and albuminoid ammonia will be quite different in 

 the second case from what they are in the first. Nevertheless the 

 author believes it is nearly universal practice to not examine 

 samples of water chemically until the second or third day after 

 collection, by which time, unfortunately, such changes have taken 

 place in many cases as to render any deductions from the amounts 

 of free and albuminoid ammonia present relatively worthless. 



